Firearm systems and methods

ABSTRACT

A firearm can have a bolt having a plurality of locking lugs that are configured to have a shear area that is larger than that of a standard M16/M4. A bolt carrier can have a bolt that has a double cut cam having an unlocking cam surface that has sufficient dwell increase to delay a start of unlocking when the bolt carrier is used in an M4 carbine. A stepped extractor pin may be provided that prevents disengagement of the extractor pin. A tube can be configured to provide gas from a barrel of the firearm to the piston via the carrier key. The tube can have a heat radiator formed from triangular shaped threads on at least a portion of the tube. A piston on the bolt and can have a plurality of rings including pairs of mating rings that are formed and maintained as a matched pair.

PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No.15/284,453 filed Oct. 3, 2016, which is a continuation of U.S. patentapplication Ser. No. 14/720,713 filed May 22, 2015, which is acontinuation-in-part of U.S. patent application Ser. No. 13/348,871filed Jan. 12, 2012, which are hereby incorporated by reference in theirentirety. U.S. patent application Ser. No. 13/348,871 claims the benefitof U.S. Provisional Application No. 61/433,092, filed Jan. 14, 2011.U.S. patent application Ser. No. 13/348,871 claims the benefit of U.S.Provisional Application No. 61/433,083, filed Jan. 14, 2011. U.S. patentapplication Ser. No. 13/348,871 claims the benefit of U.S. ProvisionalApplication No. 61/478,439, filed Apr. 22, 2011. U.S. patent applicationSer. No. 13/348,871 claims the benefit of U.S. Provisional ApplicationNo. 61/479,194, filed Apr. 26, 2011. U.S. patent application Ser. No.13/348,871 claims the benefit of U.S. Provisional Application No.61/498,426, filed Jun. 17, 2011. U.S. patent application Ser. No.13/348,871 claims the benefit of U.S. Provisional Application No.61/528,062, filed Aug. 26, 2011. All of the above-mentioned applicationsare hereby incorporated by reference in their entirety.

TECHNICAL FIELD

One or more embodiments of the invention relate generally to firearmsand, more particularly for example, to a firearm such as a member of theM16/M4 family of firearms that has features which enhance thereliability thereof.

BACKGROUND

The M16 service rifle and the M4 carbine are well known. Although thesefirearms have proven generally satisfactory, the M16 and M4, as well asother firearms, have a variety of reliability shortcomings. Thesereliability shortcomings can result in a malfunction of the firearm.These reliability shortcomings are becoming more evident as the use ofhigher capacity magazines increases. Such malfunctions can have seriousconsequences and are thus highly undesirable. Some of the reliabilityshortcomings are discussed below.

Gas operated firearms use some of the gas from a cartridge being firedto extract the spent case of the cartridge and to chamber a newcartridge. The gas travels from a port in the barrel to a gas cylinderwhere the gas pushes a piston within the gas cylinder to operate amechanism for extracting the spent case and for chambering the newcartridge. In some firearms, such as the M16 and the M4, the gascylinder is formed in the bolt carrier and the piston is part of thebolt. In such firearms, gas is provided from the barrel to the gascylinder by a gas tube.

In other firearms, such as the HK416, a separate (not part of the bolt)piston is used. The piston is disposed in a gas cylinder that is notpart of the bolt carrier. This separate piston applies force through atappet or operating rod and a bolt carrier to operate the mechanism forextracting the spent case and for chambering the new cartridge.

Whether or not the piston is part of the bolt, it is desirable toprevent gas leakage between the piston and the cylinder. Contemporarygas operated firearms commonly use a plurality of piston rings which fitinto a groove of the piston in an attempt to provide a gas seal betweenthe piston and the cylinder to mitigate gas leakage. For example, theM16, M4, and HK416 use three rings. Each of the rings is a split ringthat has a gap formed therein to facilitate installation of the ring andto allow the ring to apply an outward spring force that tends to sealthe loose fit between the piston and the cylinder.

Contemporary rings possess inherent deficiencies which detract fromtheir overall effectiveness and desirability. For example, the gaps ofthe three rings occasionally line up in a manner that allows hot gassesto flow readily through the gaps and thereby undesirably bypass therings. When the hot gases flow through the gaps, the force provided bythe gases to extract a spent case from the chamber and to chamber a newcartridge is undesirably reduced. Further, when the hot gases flowthrough the gaps, the hot gases can burn the ends of the rings andthereby undesirably enlarge the gaps. It is desirable to provide ringsthat mitigate undesirable gas flow thereby.

Contemporary gas tubes possess inherent deficiencies which detract fromtheir effectiveness and desirability. For example, contemporary gastubes can overheat and lose strength, particularly during sustainedfully automatic fire of the firearm. The higher level of heat associatedwith sustained fully automatic fire can result in undesirable thermalexpansion of the gas tube both radially and longitudinally. Such thermalexpansion can be substantially beyond an amount that can be accommodatedby the available space in the firearm. Such thermal expansion can resultin sliding/clearance fits becoming interference fits. That is, a slidingfit can undesirably become a non-sliding fit, i.e. can freeze or jam.When the gas tube heats up excessively, the weakened and expanded gastube can bend and be damaged because it is not free to slide, thuscausing the firearm to become inoperative. It is desirable to providemethods and systems for mitigating overheating in gas operated firearms.

Forward and rearward bouncing of the bolt carrier can cause the cyclicrate of a firearm to increase substantially. This increase in the cyclicrate can reduce the reliability of the firearm and can increased wear onthe firearm. It is desirable to provide methods and systems formitigating both forward and rearward bouncing of the bolt carrier.

The gas port of a contemporary M16/M4 firearm is subject to erosioncaused by bullet scrubbing and propellant bombardment. Such erosionresults in enlargement of the gas port and consequently an undesirableincrease in the cyclic rate of the firearm over time. M4 carbines, whichhave the gas port located at a rear band of the front sight, areparticularly susceptible to such erosion. This undesirable increase inthe cyclic rate can eventually result in malfunction and damage to thefirearm. It is desirable to provide for the placement of the gas portand metering of gas in a manner that does not result in an increasedcyclic rate over time.

Gas operated firearms, such as those of the M16/M4 family of firearms,have bolt and barrel locking lugs that secure the bolt to the barrelduring firing. Failure of the locking lugs can result in the firearmbeing inoperable. It is desirable to provide more robust locking lugsfor such firearms, so as to mitigate the undesirable occurrence offailure.

The cam of a bolt carrier of such firearms cooperates with the cam pinof the bolt to lock and unlock the locking lugs. In instances wherepressure of the gas system has increased and the cyclic rate hasconsequently also increased, such as due to erosion of the gas port, thecam can cooperate with the cam pin to attempt to unlock the locking lugstoo early in the firing cycle. In this instance, the gas pressure in thechamber can be too high to allow the locking lugs to rotate fully. Whenthis happens, one or more of the locking lugs can break. Again, this canresult in the firearm being inoperable, thereby potentially resulting inloss of life in situations such as during police use and battlefieldoperations. It is desirable to assure that the gas pressure in thechamber is sufficiently low to allow the locking lugs to rotate fullywhen the bolt is being unlocked.

These reliability shortcomings of such contemporary firearms can resultin the failure thereof. The failure of the firearm, particularly duringcritical police use and battlefield operations, can result in loss oflife. Therefore, it is desirable to provide firearms that do not sufferfrom these reliability shortcomings.

BRIEF SUMMARY

In accordance with embodiments further described herein, methods andsystems are provided for enhancing the reliability of firearms, such asfirearms in the M16/M4 family of firearms. For example, an embodimentcan comprise a firearm having a bolt with a plurality of locking lugsthat are configured to have a shear area that is at least approximately1.3 times that of a standard M16/M4. A piston can be formed on the boltand can have a plurality of rings that are configured to cooperate withthe piston to mitigate gas leakage past the piston. Each of the ringscan have a key formed thereon and a gap formed therein such that the gapof one ring is configured to receive at least a portion of the key ofanother ring. A bolt carrier can have the bolt movably attached thereto.The bolt carrier can have a double cut cam. The double cut cam can havea starting point in an unlocked position of the bolt that issubstantially the same as the standard M16 cam and can have an unlockingcam surface that has sufficient dwell to increase to delay a start ofunlocking when the bolt carrier is used in an M4 carbine. Thus, thedwell can be increased with respect to an M4 carbine lacking a doublecut cam. A weight can be movably disposed within the bolt carrier. Theweight can be configured to inhibit rearward and forward bouncing of thebolt carrier. A long stroke carrier key can be attached to the boltcarrier and can be configured to facilitate a stroke of the bolt carrierthat is approximately 0.360 inch longer than that of a standard M16/M4.A gas tube can be configured to provide gas from a barrel of the firearmto the piston via the carrier key. The gas tube can have a heat radiatorformed on at least a portion of the gas tube. A gas metering plug canhave a gas metering hole configured to meter gas from the barrel of thefirearm to the bolt carrier of the firearm. The gas metering hole can belocated away from a gas port of the firearm. A front sight block canhave a rear band and a front band for attaching the front sight block tothe barrel and can have a gas passage formed in the front band forfacilitating gas flow from the barrel to a gas tube of the firearm.

According to an embodiment, the bolt carrier assembly may have a boltcarrier with an unlocking cam surface that has sufficient dwell increaseto delay the start of unlocking when the bolt carrier is used in an M4carbine. The lengthened cam is such that when the bolt relative to thebolt carrier is in its most forward unlocked position, the bolt'sextractor pin may be fully exposed and not retained by the bolt carrier,thus, the extractor pin is stepped so that, in combination with thebolt's extractor spring and extractor, acts as a detent to retain theextractor pin.

According to an embodiment, a bolt group can have a bolt having aplurality of locking lugs. The locking lugs can be configured to have ashear area that is at least approximately 1.3 times that of a standardM16/M4. A piston can be formed on the bolt and can have a plurality ofrings configured to cooperate with the piston to mitigate gas leakagepast the piston. Each of the rings can have a key formed thereon and agap formed therein such that the gap of one ring is configured toreceive at least a portion of the key of another ring. A bolt carriercan have the bolt movably attached thereto. The bolt carrier can have adouble cut cam. The double cut cam having a starting point in anunlocked position of the bolt that is substantially the same as thestandard M16 cam and can have an unlocking cam surface that hassufficient dwell increase to delay a start of unlocking when the boltcarrier is used in an M4 carbine. Thus, the dwell can be increased withrespect to an M4 carbine lacking a double cut cam. A weight can bemovably disposed within the bolt carrier. The weight can be configuredto inhibit rearward and forward bouncing of the bolt carrier. A carrierkey can be attached to the bolt carrier and can be configured tofacilitate a stroke of the bolt carrier that is approximately 0.360 inchlonger than that of a standard M16/M4.

According to an embodiment, a bolt carrier assembly for use in an M4carbine having a bolt with extended locking lugs and the lengthened boltis such that when the bolt relative to the bolt carrier is in its mostforward unlocked position the bolt's extractor pin is fully exposed andnot retained by the bolt carrier, the extractor pin is stepped so thatin combination with the bolt's extractor spring and extractor acts as adetent to retain the extractor pin.

According to an embodiment, a barrel extension for use in an M4 carbinewith extended locking lugs which require a lengthened bolt such thatwhen the bolt relative to the bolt carrier is in its most forwardunlocked position the bolt's extractor pin is fully exposed and notretained by the bolt carrier, the extractor pin is stepped so that incombination with the bolt's extractor spring and extractor acts as adetent to retain the extractor pin.

According to an embodiment, a barrel extension for use in an M4 carbineis provided with extended locking lugs and longer less steep feed rampsthan the standard M4 locking lugs and feed ramps to reduce bullet bounceoff the feed ramp.

According to an embodiment, a bolt carrier may have a shortened key forincreased travel to maintain the M4's original bolt catch over travel.

According to an embodiment, a ring can be configured to be received atleast partially within a groove of the piston. A key can be formed uponthe ring and a gap can be formed in the ring. The gap of one ring can beconfigured to receive at least a portion of the key of another ring.Thus, the rings can be interlocked such they cannot rotate to a positionwhere the gaps line up in a manner that allows hot gasses to flowthrough the gaps.

According to an embodiment, a gas tube can be configured to provide gasfrom a barrel of a firearm to a piston of the firearm. A heat radiatorcan be formed on at least a portion of the gas tube, according to anembodiment. The heat radiator can inhibit overheating of the gas tube.The gas tube can be configured such that thermal expansion does notcause the gas tube to bind or be damaged by cycling of the firearm.

According to an embodiment, a tube may provide gas from a barrel of afirearm to a piston of the firearm. A heat radiator may extend from atleast a portion of the tube and may have threads.

According to an embodiment, the threads may be formed on a portion ofthe tube away from ends of the tube.

According to an embodiment, the tube is configured for use on a firearmhaving a piston formed on a bolt of the firearm, such as a member of anM16/M4 family of firearms.

According to an embodiment, the gas tube may receive gas from a barrelof the firearm via a front sight of the firearm and may provide the gasto a bolt carrier of the firearm via a bolt carrier key. The tube mayhave an outside interfacing diameter to the bolt carrier key of lessthan 0.1792 inches. The tube may have a length from a front sightmounting hole thereof to a rear end thereof of less than 9.57 inches foran M4 type of firearm or the tube may have a length from a front sightmounting hole thereof to a rear end thereof of less than 14.95 inchesfor an M16 type of firearm.

According to an embodiment, a method may include cutting a tube; forminga radiator on the tube; and installing the tube on a firearm such thatthe tube is configured to provide gas from a barrel of the firearm to apiston thereof.

According to an embodiment, the method may include the heat radiatorhaving threads.

According to an embodiment, a tube may receive gas from a barrel of afirearm that is a member of an M16/M4 family of firearms via a frontsight of the firearm and may provide the gas to a bolt carrier of thefirearm via a bolt carrier key. The tube may have an outside interfacingdiameter to the bolt carrier key of less than 0.1792 inches.

According to an embodiment, a tube may receive gas from a barrel of afirearm that is a member of an M4 family of firearms via a front sightof the firearm and may provide the gas to a bolt carrier of the firearmvia a bolt carrier key. The tube may have a length from a front sightmounting hole thereof to a rear end thereof of less than 9.57 inches.

According to an embodiment, a tube may receive gas from a barrel of afirearm that is a member of an M16 family of firearms via a front sightof the firearm and may provide the gas to a bolt carrier of the firearmvia a bolt carrier key. The tube may have a length from a front sightmounting hole thereof to a rear end thereof of less than 14.95 inches.

According to an embodiment, a device can comprise a gas metering plughaving a gas metering hole that is configured to meter gas from a barrelof a firearm to a bolt carrier of the firearm. The gas metering hole canbe located away from a gas port of the firearm, so as not to be subjectto erosion caused by bullet scrubbing and propellant bombardment.

According to an embodiment, undesirable forward and rearward bouncing ofa bolt carrier of a gas operated firearm can be inhibited. For example,a device can have a bolt carrier and an anti-bounce weight movablydisposed within the bolt carrier. The weight can be configured toinhibit both rearward and forward bouncing of the bolt carrier.

According to an embodiment, a bolt carrier can have a double cut camformed therein. The double cut cam can have a starting point in anunlocked position of the bolt that is substantially the same as thestandard M16 cam. The double cut cam can have an unlocking cam surfacethat has sufficient dwell increase to delay a start of unlocking whenthe bolt carrier is used in an M4 carbine.

According to an embodiment, a bolt and a barrel extension for an M16/M4firearm can have a plurality of locking lugs. The locking lugs can beconfigured to have a shear area that is at least approximately 1.3 timesthat of a standard M16/M4. A carrier key can be configured to facilitatea stroke of the bolt carrier that is approximately 0.360 inch longerthan that of a standard M16/M4. A buffer can be configured to limittravel of the bolt carrier. The buffer can be approximately 0.360 inchshorter than that of the standard M16/M4.

According to an embodiment, the gas port of a firearm can be movedforward along the barrel so as to delay the time at which gas acts uponthe bolt of the firearm after a cartridge is fired and so as to reducethe pressure of the gas acting upon the bolt. In this manner, the cyclicrate of the firearm can be reduced and the reliability of the firearmcan be enhanced.

These features can cooperate to provide a safer, more reliable firearm.For example, the long or extended locking lugs, gas piston rings, andthe gas tube can cooperate to make the gas system of the firearm morerobust. As a further example, the anti-bounce weight, the gas meteringplug, the gas passage in the forward sight band and double cut cam cancooperate to reduce the cyclic rate and to mitigate undesirable wear onthe firearm.

The scope of the disclosure is defined by the claims, which areincorporated into this section by reference. A more completeunderstanding of embodiments will be afforded to those skilled in theart, as well as a realization of additional advantages thereof, by aconsideration of the following detailed description of one or moreembodiments. Reference will be made to the appended sheets of drawingsthat will first be described briefly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a bolt, such as for an M16/M4, showingkeyed piston rings exploded therefrom, according to an embodiment.

FIG. 2 is an enlarged side view of a piston of FIG. 1 having one keyedpiston ring installed thereon and one keyed piston ring partiallyinstalled thereon, according to an embodiment.

FIG. 3 is an enlarged perspective view of the piston of FIG. 1 havingtwo keyed piston rings installed thereon, according to an embodiment.

FIG. 4 is a perspective view of a piston, such as for a HK416, showingkeyed piston rings exploded therefrom, according to an embodiment.

FIG. 5 is an enlarged side view of the piston of FIG. 4 having one keyedpiston ring installed thereon and one keyed piston ring partiallyinstalled thereon, according to an embodiment.

FIG. 6 is an enlarged perspective view of the piston of FIG. 4 havingtwo keyed piston rings installed thereon, according to an embodiment.

FIG. 7 is a perspective view of a firearm, such as an M16/M4, having thebolt of FIG. 1, according to an embodiment.

FIG. 8A is a perspective view of a firearm, such as a HK416, having thepiston of FIG. 4, according to an embodiment.

FIGS. 8B-E are various views of a keyed piston ring, according to anembodiment.

FIG. 9 is side view of a heat dissipating gas tube for a firearm,according to an embodiment.

FIGS. 10A-10C are cross-sectional views showing the heat dissipating gastube and a gas metering plug, according to an embodiment.

FIG. 11 is a cross-sectional side view of a rear end of the gas tube anda carrier key that receives the rear end of the gas tube, according toan embodiment.

FIG. 12 is a flow chart showing a method for making a firearm having aheat dissipating gas tube, according to an embodiment.

FIG. 13A is a top view of a bolt carrier having an anti-bounce assembly,according to an embodiment.

FIG. 13B is a front view of a stepped extractor pin, according to anembodiment.

FIG. 13C a cross-sectional view of the stepped extractor pin disposed ina bolt, according to an embodiment.

FIG. 13D is a cross-sectional view of a stepped extractor pin disposedin a bolt, according to an embodiment.

FIG. 13E is a side view of a bolt carrier assembly with a steppedextractor pin, according to an embodiment.

FIG. 14 is a side view of the bolt carrier of FIG. 13A, according to anembodiment.

FIG. 15 is an enlarged side view of the anti-bounce assembly of FIG. 13Ashowing an anti-bounce weight in a zero or non-impact position,according to an embodiment.

FIG. 16 is an enlarged side view of the anti-bounce assembly of FIG. 13Ashowing the anti-bounce weight in a rearward impact position, accordingto an embodiment.

FIG. 17 is an enlarged side view of the anti-bounce assembly of FIG. 13Ashowing the anti-bounce weight in a forward impact position, accordingto an embodiment.

FIG. 18 is an exploded view of the bolt carrier of FIG. 13A, accordingto an embodiment.

FIG. 19 is a top exploded view of plungers, springs, and the anti-bounceweight of FIG. 18, according to an embodiment.

FIG. 20 is a perspective exploded view of the plungers, the springs, andthe anti-bounce weight of FIG. 18, according to an embodiment.

FIG. 21 is a top assemble view of the plungers, the springs, and theanti-bounce weight of FIG. 18, according to an embodiment.

FIG. 22 is a perspective assembled view of the plungers, the springs,and the anti-bounce weight of FIG. 18, according to an embodiment.

FIG. 23 is a perspective view of a modified bolt carrier, according toan embodiment.

FIG. 24 is an end view of the modified bolt carrier of FIG. 23,according to an embodiment.

FIG. 25 is a side view of an anvil of FIG. 23, according to anembodiment.

FIG. 26 is an end view of the modified bolt carrier of FIG. 23 showingan impact area and a bearing area, according to an embodiment.

FIG. 27 is an end view of the modified bolt carrier of FIG. 23 showing aplunger, according to an embodiment.

FIGS. 28A-28C are various views of the anti-bounce assembly, accordingto an embodiment.

FIGS. 29A-29C are various views of the anti-bounce weight, according toan embodiment.

FIGS. 30A-30D are various views of the plunger, according to anembodiment.

FIGS. 31A-31C are various views of the anvil, according to anembodiment.

FIGS. 32A-32F are various views showing a bolt carrier modification,according to an embodiment.

FIGS. 33A and 33B are various views showing a double cut cam, accordingto an embodiment.

FIG. 34A-34P are various views showing a carrier key, according to anembodiment.

FIG. 35 is a cross-sectional side view of a portion of a standard, i.e.contemporary, M16/M4 5.56 mm firearm with the bolt group shown in itsfull forward position and full rear position.

FIG. 36A is a cross-sectional side view of a portion of an M16/M4 5.56mm and 6.8 mm firearm having a bolt and barrel extension with morerobust extended locking lugs and other improved features, with the boltgroup shown in two positions, according to an embodiment.

FIGS. 36B-36Y are various views of extended locking lugs of a boltcarrier assembly, according to an embodiment.

FIG. 37A is an enlarged cross-sectional side view showing the lockinglugs of both the standard M16/M4 5.56 mm firearm (upper portion) and themore robust extended locking lugs of the improved M16/M4 5.56 mm and 6.8mm firearm (lower portion), according to an embodiment.

FIG. 37B is an enlarged side view showing the barrel extensions of boththe standard M16/M4 5.56 mm firearm (upper barrel extension) and thebarrel extension of the improved M16/M4 5.56 mm and 6.8 mm firearm(lower barrel extension), according to an embodiment.

FIG. 38 is an end view showing the feed ramps of a standard, i.e.contemporary, M16/M4 5.56 mm firearm.

FIG. 39 is an end view showing the feed ramps of the M16/M4 5.56 mm and6.8 mm firearm, according to an embodiment.

FIG. 40 shows the front sight block and gas tube of a standard, i.e.contemporary, M4 carbine.

FIG. 41 shows a metering plug installed in a front sight block havingthe gas port in the standard location and showing the use of a thickwall gas tube, according to an embodiment.

FIG. 42 shows a metering plug installed in a front sight block havingthe gas port moved to a forward location and showing the use of a thickwall gas tube, according to an embodiment.

FIG. 43 shows a metering plug installed in a front sight block havingthe gas port moved to a forward location (with an enlarged view of theinstalled metering plug) and showing the use of a thick wall gas tube,according to an embodiment.

FIG. 44 shows a metering plug installed in a front sight block havingthe gas port moved to a forward location (with an enlarged view of theuninstalled metering plug and gas tube) and showing the use of a thickwall gas tube, according to an embodiment.

FIG. 45 shows the anti-bounce weight having a chamfer formed thereon toprovide clearance for the hammer, according to an embodiment.

FIG. 46 shows a cam pin having a chamfer formed thereon to provideclearance for the cam, according to an embodiment.

Embodiments of the present invention and their advantages are bestunderstood by referring to the detailed description that follows. Itshould be appreciated that like reference numerals are used to identifylike elements illustrated in one or more of the figures.

DETAILED DESCRIPTION

Methods and systems are provided for enhancing the reliability offirearms, such as firearms in the M16/M4 family of firearms. Forexample, according to an embodiment a firearm can have a bolt having aplurality of extended locking lugs that are configured to have a sheararea that is at least approximately 1.3 times that of a standard M16/M4.

A piston can be formed on the bolt and can have a plurality of ringsthat are configured to cooperate with the piston to mitigate gas leakagepast the piston. Each of the rings can have a key formed thereon and agap formed therein such that the gap of one ring is configured toreceive at least a portion of the key of another ring.

A bolt carrier can have the bolt movably attached thereto. The boltcarrier can have a double cut cam. The double cut cam can have astarting point in an unlocked position of the bolt that is substantiallythe same as the standard M16 cam and can have an unlocking cam surfacethat has sufficient dwell increase to delay a start of unlocking whenthe bolt carrier is used in an M4 carbine (as compared to the delayprovided by the standard cam surface). This delay can be as little as0.00016 seconds, for example. This delay is based on the time it takesfor a 62 grain M855 bullet to travel 5.5 inches beyond the gas port inan M16 rifle barrel at an average velocity of 3056 feet per second.During this time the chamber pressure significantly drops in the rifle,but not in the carbine which has the gas port 5½ inches closer to thechamber that does the rifle, thus causing the gas to start to act on thegas system 0.00016 seconds sooner in the carbine than in the rifle. Thedwell is increased so as to regain the 0.00016 second delay and thebeneficial pressure drop that is present in the rifle and not in thestandard carbine. The additional dwell needed in the cam is 0.036 inchesif the carrier is at full velocity of 20 feet per second, which is 153times slower than the bullet since 5.5 inches divided by 153=0.036inches. Thus, the 0.062 inch dwell increase is more than significant.

The 0.062 additional dwell has two advantages. It provides the timeneeded to reduce chamber pressure that tends to bind the locking lugs atthe start of unlocking and it allows 0.062 additional bolt carrierbounce before safely retracting the firing pin thus reducing the chanceof a misfire from occasional carrier bounce.

A weight can be movably disposed within the bolt carrier. The weight canbe configured to inhibit rearward and forward bouncing of the boltcarrier. A carrier key can be attached to the bolt carrier and can beconfigured to facilitate a stroke of the bolt carrier that isapproximately 0.360 inch longer than that of a standard M16/M4. A gastube can be configured to provide gas from a barrel of the firearm tothe piston via the carrier key. The gas tube can have a heat radiatorformed on at least a portion of the gas tube.

A gas metering plug can have a gas metering hole configured to meter gasfrom the barrel of the firearm to the bolt carrier of the firearm. Thegas metering hole can be located away from a gas port of the firearm. Afront sight block can have a rear band and a front band for attachingthe front sight block to the barrel and can have a gas passage formed inthe front band for facilitating gas flow from the barrel to a gas tubeof the firearm. These, as well as other features, and their advantagesare discussed in detail herein.

The cooperation of these features can provide a safer, more reliablefirearm. For example, the long or extended locking lugs, gas pistonrings, and the gas tube can cooperate to make the gas system of thefirearm more robust. As a further example, the anti-bounce weight, gasmetering plug, gas passage in the forward sight band and the double cutcam can cooperate to reduce the cyclic rate and to better facilitate theuse of the extended locking lugs.

Methods and systems for inhibiting undesirable gas leakage and/or heatbuild up in a gas operated firearm are disclosed. According to anembodiment, a pair of rings can be configured to interlock with respectto one another such that the rings rotate within a groove of a piston ofa gas system of a firearm. Since the rings rotate in unison, they do notalign in a manner that readily facilitates undesirably increased gasflow past the piston. Such rings can generally be used with both M16/M4and HK416 types of firearms.

According to an embodiment, a gas tube that better tolerates the heatassociated with sustained fully automatic fire of a firearm isdisclosed. The gas tube is less prone to overheating and betteraccommodates thermal expansion. Thus, the firearm cycles and fires moreuniformly and is more reliable. Such a gas tube can generally be usedwith M16/M4 types of firearms and generally cannot be used with HK416types of firearms since the HK416 types of firearms use a substantiallydifferent gas system.

According to an embodiment, methods and systems are provided forinhibiting undesirable forward and rearward bouncing of a bolt carrierof a gas operated firearm, such as a fully automatic gas operatedfirearm. An anti-bounce assembly, including an anti-bounce weight, canmitigate undesirable speeding up of the cyclic rate of a firearm due togas port erosion and can thus reduce wear and increase the reliabilityof the firearm.

According to an embodiment, a gas metering port can prevent the cyclicrate of the firearm from increasing undesirably as the gas port erodes.The gas port can be moved forward, from the rear sight band to theforward sight band, to reduce pressure in the gas system and to reducethe cyclic rate of the firearm.

According to an embodiment, stronger extended locking lugs on the boltand on the barrel extension can be provided to prevent breakage thereof.The extended locking lugs are particularly useful when the firearm isbeing operated with cartridges providing higher chamber pressures. Adouble cut cam can provide increased dwell such that the pressure in thechamber has time to decrease to a point where the locking lugs (whetherextended locking lugs or standard locking lugs) can be more reliably andsafely disengaged.

Examples of embodiments of keyed gas piston rings are discussed indetail below. Examples that are suitable for use with the M16/M4 rifleare discussed with reference to FIGS. 1-3 and 7. Examples that aresuitable for use with the HK416 rifle are discussed with reference toFIGS. 4-6 and 8. The gas piston of the M16 and the M4 is an integratedpart of the bolt that is slidably disposed within a gas cylinder formedin the bolt carrier of the firearm. The gas cylinder, i.e. the boltcarrier, moves with respect to the gas piston.

FIG. 1 is a perspective view of a bolt 100 of a gas operated firearm 700(FIG. 7), according to an embodiment. The bolt 100 can be a bolt of anM16 rifle or an M4 carbine, for example. The bolt 100 can have a piston101 formed thereon. A groove 102 can be formed circumferentially aroundthe piston 101. A pair of rings 105 are shown exploded from the bolt100. The rings 105 can comprise a first ring 105 a and a second ring 105b. The rings 105 can be configured to be received at least partiallywithin the groove 102 of the piston 101 of the gas operated firearm 700.

A key 108 can be formed upon each of the rings 105. The key 108 canextend generally perpendicularly with respect to a plane of each of therings 105. The key 108 can have a generally rectangular cross-sectionwhen taken in either of two generally orthogonal planes. That is thewalls of the ring can generally define a rectangle.

A gap 107 can be formed in each of the rings 105. The gap 107 of eachone of the rings 105 can be configured to receive at least a portion ofthe key 108 of another one of the rings 105. The gap 107 can have agenerally rectangular cross-section when taken in either of twogenerally orthogonal planes. Thus, a pair of the rings 105 can beconfigured to interlock with one another such that the two rings 105 canrotate, but can only rotate substantially in unison with respect to oneanother.

In an embodiment, the key 108 and the gap 107 of each of the rings 105can be formed such that a pair of the rings 105 are nestable with thekey 108 of each one of the rings 105 being disposed within the gap 107of each other one of the rings 105 while the rings 105 are substantiallyflush with respect to one another. The nesting of the rings 105interlocks the rings 105 such that the rings 105 rotate in unison.

In an embodiment, the gaps 107 of the two rings 105 can be diametricallyopposed with respect to one another when the rings 105 are interlocked.Since the two rings 105 rotate substantially in unison, the gaps 107 donot align in a fashion that facilitates increased gas flow past therings 105.

In an embodiment, the rings 105 can be formed of stainless steel. Forexample, the rings 105 can be formed of 17-4 stainless steel. Variousother materials, including refractory materials such as ceramics, arecontemplated.

In an embodiment, the groove 102 can be substantially rectangular incross-section. In an embodiment, the rings 105 can also be substantiallyrectangular in cross-section and thus can be generally complementary insize and shape with respect to the groove 102.

FIG. 2 is an enlarged side view of the piston 101 having the first ring105 a completely installed thereon and having the second ring 105 bpartially installed thereon, according to an embodiment. The rings 105can be temporarily bent or spring deformed in order to slide over thepiston 101 and into the groove 102. The key 108 of the second ring 105 bis positioned to be received at least partially within the gap 107 ofthe first ring 105 a.

FIG. 3 is an enlarged perspective view of the piston 101 having tworings 105 installed thereon, according to an embodiment. The two rings105 are seated within the groove 102. The key 108 of the second ring 105b is disposed at least partially within the gap 107 of the first ring105 a and the key 108 of the first ring 105 a is disposed at leastpartially within the gap 107 of the second ring 105 b.

The piston of an HK416 is disposed in a gas cylinder of a firearm 800(see FIG. 8A) rather than in a cylinder of the bolt carrier as discussedherein with respect to the M16/M4. FIGS. 4-6 show a system forinhibiting undesirable gas flow around the piston of an HK416 or thelike and are discussed in detail below.

FIG. 4 is a perspective view of the piston 400 of a gas operated firearm800 (FIG. 8A), according to an embodiment. The piston 400 can be apiston of an HK416 rifle, for example. A groove 402 can be formedcircumferentially around the piston 400. A pair of rings 405 are shownexploded from the piston 400. The rings 405 can comprise a first ring405 a and a second ring 405 b. The rings 405 can be configured to bereceived at least partially within the groove 402.

A key 408 can be formed upon each of the rings 405. The key 408 canextend generally perpendicularly with respect to a plane of the rings405. The key 408 can have a generally rectangular cross-section whentaken in either of two generally orthogonal planes.

A gap 407 can be formed in each of the rings 405. The gap 407 of eachone of the rings 405 can be configured to receive at least a portion ofthe key 408 of another one of the rings 405. The gap 407 can have agenerally rectangular cross-section when taken in either of twogenerally orthogonal planes. Thus, a pair of the rings 405 can beconfigured to interlock with one another such that the two rings 405 canrotate, but can only rotate substantially in unison with respect to oneanother.

In an embodiment, the key 408 and the gap 407 of each ring 405 can beformed such that a pair of the rings 405 are nestable with the key 408of each of the rings 405 being disposed at least partially within thegap 407 of each other of the rings 405 while the rings 405 aresubstantially flush with respect to one another. The nesting of therings 405 interlocks the rings 405 such that the rings 405 rotate inunison.

In an embodiment, the gaps 407 of the two rings 405 can be diametricallyopposed with respect to one another when the rings 405 are interlocked.Since the two rings 405 rotate substantially in unison, the gaps 407 donot align in a fashion that facilitates increased gas flow past therings 405.

In an embodiment, the rings 405 can be formed of stainless steel. Forexample, the rings 405 can be formed of 17-4 stainless steel. Variousother materials, including refractory materials such as ceramics, arecontemplated.

In an embodiment, the groove 402 can be substantially rectangular incross-section. In an embodiment, the rings 405 can also be substantiallyrectangular in cross-section and thus can be generally complementary insize and shape with respect to the groove 402.

FIG. 5 is an enlarged side view of the piston 400 having the first ring405 a partially installed thereon and having the second ring 405 bcompletely installed thereon, according to an embodiment. The rings 405can be temporarily bent or spring deformed in order to slide over thepiston 400 and into the groove 402. The key 408 of the second ring 405 bis positioned to be received at least partially within the gap 407 ofthe first ring 405 a.

FIG. 6 is an enlarged perspective view of the piston 400 having tworings 405 installed thereon, according to an embodiment. The two rings405 are seated within the groove 402. The key 408 of the second ring 405b is disposed at least partially within the gap 407 of the first ring405 a.

According to various embodiments, a device can comprise a first ring 105a, 405 a configured to be at least partially received within a groove102, 402 of a piston 101, 400 of a gas operated firearm 700, 800. Asecond ring 105 b, 405 b can be configured to be at least partiallyreceived within the groove 102, 402. The first ring 105 a, 405 a andsecond ring 105 b, 405 b can be configured to interlock with one anothersuch that the first ring 105 a, 405 a and second ring 105 b, 405 brotate substantially in unison within the groove 102, 402. Various meansfor effecting such interlocking are contemplated. The use of a key 108,408 and a gap 107, 407 as discussed herein are by way of example only,and not by way of limitation.

Any desired number of rings 105, 405 and any desired number of grooves102, 402 in the piston 101, 400 may be used. For example, two grooves102, 402, each containing two rings 105, 405 or three rings 105, 405apiece, may be used. Thus, various embodiments may comprise 2, 3, 4, 5,6, or more rings 105, 405.

In various embodiments, the gaps 107, 407 can be partial gaps that donot extend entirely though the rings 105, 405. For example, the gaps107, 407 can be sufficiently sized to receive at least a portion of thekeys 108, 408 while not forming a separation in the rings 105, 405.Thus, the gaps 107, 407 may be depressions, indentations, or cutouts,for example. Any desired number and configuration of the gaps 107, 407and the keys 108, 408 can be used. The gaps 107, 407 and the keys 108,408 can be generally complementary with respect to one another. The gaps107, 407 and the keys 108, 408 can be non-complementary with respect toone another.

The piston rings 105, 405 need not be received within a groove 102, 402of the piston 101, 400. Rather, the piston rings 105, 405 can be placedupon the piston 101, 400 and can be held in position by any means orstructure desired. The piston rings 105, 405 can cooperate with thepiston 101, 400 to mitigate gas leakage past the piston 101, 400.

According to an embodiment, the piston 400 can be configured to fitwithin a gas cylinder of a firearm 800 that does not have the piston 400formed upon a bolt of the firearm 800, for example. The piston 400 canbe configured to fit within a gas cylinder of a HK416 type of firearm800.

Alternatively, the piston 101 can be formed upon a bolt 100 of thefirearm 700. The gas cylinder can be formed in a bolt carrier of thefirearm 700. The piston 101, 400 can fit within a gas cylinder of anM16/M4 type of firearm, for example.

FIG. 7 is a perspective view of the firearm 700 having the piston 101formed on the bolt 100, according to an embodiment. The firearm 700 canbe an M16 or an M4, for example. The firearm 700 can have one or morepairs of rings 105 disposed in one or more grooves 102 about the piston101 thereof to mitigate gas leakage past the piston 101, as discussedherein.

FIG. 8A is a perspective view of a firearm 800 having the piston 400,according to an embodiment. The firearm 800 can be an HK416, forexample. The firearm 800 can have one or more pairs of rings 405disposed about the piston 400 thereof to mitigate gas leakage past thepiston 400, as discussed herein.

In operation, a shooter fires the firearm 700, 800 and hot, highpressure gas is provided by the cartridge. As shown in FIG. 7 for an M16or M4 type of rifle, the gas travels through a front sight (FIG. 40) tothe gas tube 705, then through the gas tube 705 and a carrier key 752 tothe bolt carrier 702, where the gas moves the bolt carrier 702, andconsequently the bolt 100, so as to effect extraction of the spentcartridge and chambering of a new cartridge. The bolt 100 is disposedwithin a gas cylinder 701 formed in the bolt carrier 702. As shown inFIG. 8A for an HK416 type of rifle, the gas moves the piston 400 withinthe gas cylinder 801 so as to move a tappet or operating rod 802 toeffect extraction of a spent cartridge and chambering of a newcartridge.

In either instance, the use of rings 105, 405 having gaps 107, 407 andkeys 108, 408 that facilitate nesting or interlocking of the rings 105,405 substantially mitigates undesirable gas flow past the piston 101,400. The nested or interlocked rings 105, 405 provide increasedresistance to such gas flow by preventing the gaps 107, 407 fromaligning with respect to one another. For example, gas can besubstantially forced to follow a longer and more contorted path underthe rings 105, 405 from which the gas reemerges to flow past the piston101, 400. This longer and more contorted path around four cornerssubstantially inhibits such gas flow and consequently inhibits gasleakage past the piston 101, 400.

Firearms 700 that have the piston 101 formed on the bolt 100 thereof canbe referred to herein as M16/M4's, or M16/M4 types of firearms, ormembers of an M16/M4 family of firearms. Firearms 800 that do not havethe piston 400 formed on a bolt thereof can be referred to herein asHK416's, HK416 types of firearms, or members of an HK416 family offirearms.

Thus, according to one or more embodiments, two rings 105, 405 can benested such that undesirable gas leakage past the piston 101, 400 issubstantially inhibited. In this manner, damage to the rings can besubstantially mitigated and fouling of components of the firearm 700,800, such as within the receiver thereof, can be substantiallymitigated. By inhibiting gas leakage past the piston 101, 400reliability of the firearm is substantially enhanced and operation ofthe firearm is made more uniform.

Anticipating that 60-shot and 100-shot magazines may soon replace thecurrent standard 30-shot M16/M4 magazines, the consequent heat problemsassociated with such increased capacity (and the resulting extendedrapid firing of the firearm) also need to be addressed. The M4 gas tube705 can soften and bend (and thus become inoperable) in as few as four100-shot bursts. The M16 gas piston rings can burn out in as few as two100-shot bursts. To mitigate such heat problems, the keyed piston rings104, 405 and a heat dissipating gas tube 705 may be used, as discussedherein.

Contemporary piston rings used in firearms such as the M16/M4 have a gapof approximately 0.05 inches or less. If the gap is larger, more of thering on the pressure side may be unsupported at the gap with the matingring. This unsupported area, if much larger than the 0.05 inches,combined with the high pressure of the gas systems will result infailure of the ring at the unsupported area. The gap, by necessity, fora keyed ring of the type described herein, to accept a key from a matingring, is wider (e.g., 0.09 inches) than for conventional rings used infirearms. If the key of the ring on the pressure side had the exactheight so that it supported the ring in the gap area to insure that thering does not flex under the high pressure, i.e. the majority of thering is flush against the mating ring and in the gap the key exactlysupports the ring so there is no flexing of the ring in the direction ofthe pressure in or next to the gap, then the ring could survive, butthis arrangement may not allow sufficient manufacturing tolerance.

In an embodiment of the present disclosure, keyed rings 805 are providedin which pairs of rings are provided as a matched set and lappedtogether so that each key 804 has a height (h) that is substantially thesame as the thickness 810 of slot 806 of its mating ring as shown inFIGS. 8B, 8C, 8D, and 8E. Key 804 may have a height (h) that is equal toring thickness 810 (e.g., height (h) may be approximately 0.000 inchesto 0.006 inches taller than ring thickness 810). In an embodiment of thepresent disclosure, key 804 height (h) and width (w) may be, forexample, approximately 0.027 inches and approximately 0.024 inches,respectively. The length (l) of key 804 may be relatively equivalent towidth 814 of ring 805. In an embodiment, adjoining surfaces 812 of ring805 and key 804 may each have a curvature. The keyed rings may cooperatewith the piston of a gas operated firearm to mitigate gas leakage pastthe piston.

In this way, the two rings may be formed and maintained as a matched set808 and may be lapped such that each key has a height that issubstantially the same as the thickness (i.e. thickness 810) of itsmating ring. The gap into which the mating key fits may span an angle ofless than approximately 30 degrees and may have a width of, for example,0.09 inches. For example, FIG. 8D shows a set of keyed rings 808 lappedtogether. The mating key may span an angular distance in a directionaround the ring of, for example, less than 10 degrees and may have awidth (w) of, for example, approximately 0.024 inches and a height (h)of approximately 0.027 inches.

More particularly, some gas operated firearms 700 use the gas tube 705to deliver high pressure, very hot, gas to the piston 101 formed uponthe bolt 100, as discussed herein. The M16 and the M4 are examples offirearms 700 that deliver gas to the piston 101 via the contemporary gastube 705. When the firearm 700 is shot repeatedly over an extendedlength of time, such as during extended fully automatic fire using aplurality of high capacity magazines, the contemporary gas tube 705 canheat up substantially. In such instances, the temperature of thecontemporary gas tube 705 can be excessive and thus undesirable damageto the contemporary gas tube 705 can result.

When the gas tube 705 heats up, the length and/or diameter of the gastube 705 can increase substantially due to thermal expansion. Suchthermal expansion can interrupt the firing cycle of the firearm 700 andthus result in the firearm 700 becoming inoperative. As such, it isdesirable to provide methods and systems for mitigating heat build upand for accommodating thermal expansion of the gas tubes 705 in gasoperated firearms.

As shown in FIG. 9, a heat dissipating gas tube 705 can have enhancedheat dissipation such that during extended fully automatic fire the gastube 705 can remain at a sufficiently low temperature as to not incursubstantial damage. The enhanced heat accommodation tends to allow thegas tube 705 to continue to function properly when heated, particularlywhen heated by sustained fully automatic fire. Examples of embodimentsof more heat tolerant and/or heat dissipating gas tubes 705 arediscussed in detail below.

FIG. 9 shows the gas tube 705 for an M16 and/or M4 type of firearm 700,according to an embodiment. The gas tube 705 can have a heat dissipaterformed thereon. For example, the gas tube 705 can have screw threads 707formed upon a substantial portion of the length of the gas tube 705.

In an embodiment of the present disclosure, the threads 707 of tube 705may form an equilateral triangle that doubles the heat radiating surfaceof the tube regardless of the thread pitch. In addition, the triangularradiating surfaces do not face each other and are thus much moreefficient than typical cooling fins which work best with air passingthrough them, which in this case is not available.

Other examples of heat dissipaters can include fins, fingers, flanges,protrusions, and any other structures that tend to increase the surfacearea of the gas tube 705 and thus enhance radiation of heat from the gastube 705. A plurality of spaced apart annular fins can substantiallyencircle the gas tube 705, for example. A plurality of longitudinal finscan extend along a length of the gas tube 705, for example. A spiral fincan extend around a length of the gas tube 705, for example. The finscan form a V-notch with approximately 60 degrees between opposing walls,for example.

The outer diameter and/or the inner diameter of the gas tube 705 can beincreased to enhance the ability of the gas tube 705 to operate underextended fully automatic fire. For example, in one embodiment, the outerdiameter of the gas tube 705 or a portion of the gas tube 705 can beincreased from the standard 0.180 inch to approximately 0.218 inch.

According to an embodiment, the threads 707 can be a uniform standardthread form, such as 1/4-32 UNEF (Unified National Extra Fine) threads,for example. The threads 707 can be helical threads, for example.Various other types of the threads 707 are contemplated. More than onetype of the threads 707 can be used. Any desired combination of thethreads 707 or types of the threads 707 can be used. In one embodiment,the threads 707 can extend along a portion of the length of the gas tube705. For example, the threads 707 can extend along a portion of the gastube 705 that is away from ends, 721 and 722, of the gas tube 705. Thus,the ends 721 and 722 of the gas tube 705 can have no threads 707 formedthereon. In one embodiment, the threads 707 can extend along the entiregas tube 705.

The threads 707 need not be conventional threads. The threads 707 neednot be any type of standard threads, e.g., threads made according to anaccepted standard. The threads 707 can be formed with a die. The threads707 can be formed by machining. The threads 707 can be formed by lasercutting. The threads 707 can be formed by any desired method.

The threads 707 can be integral with the gas tube 705. The threads 707can be formed separately from the gas tube 705 and/or can be attached tothe tube 705. The threads 707 can be formed of either the same materialas the gas tube 705 or can be formed of a different material withrespect to the gas tube 705.

In one embodiment, the threads 707 can be solely for heat dissipation.In one embodiment, the threads 707 can have another use other than heatdissipation. For example, the threads 707 can be used to mount the gastube 705 to the firearm 700. Thus, at least one end of the gas tube 705can screw into a threaded opening on the firearm 700.

The gas tube 705 can be configured to attach to a contemporary firearm700. For example, the gas tube 705 can have a first bend 711 and asecond bend 712 formed therein to facilitate mounting of the gas tube705 to a contemporary firearm 700. The first bend 711 and the secondbend 712 can align the forward end and the rearward end of the gas tube705 with their respective connections to the firearm 700. A bead 725 canbe formed on the reward end of the gas tube 705 to facilitate a desiredfit into the carrier key 752 (FIGS. 10A and 11) of the firearm 700.

In one embodiment, the gas tube 705 can be formed of stainless steel.For example, the gas tube 705 can be formed of 347 stainless steel. Inone embodiment, the gas tube 705 can be formed of a refractory material,such as a ceramic material.

The gas tube 705, and more particularly the threads 707, can have anydesired finish. For example, various textures, coatings, and treatmentsthat enhance heat dissipation are contemplated. Different parts of thegas tube 705 can have different textures, coatings, or treatments.

FIGS. 10A-10C are cross-sectional side views of portions of the firearm700 having the gas tube 705, according to an embodiment. The gas tube705 and/or the rings 105 (FIGS. 1-3) can be provided as a kit forupgrading contemporary firearms such as the M16 and M4. Thus, the gastube 705 and the rings 105 can be provided and installed together. Suchupgrading can be performed in the field, at an armory, or at amaintenance depot. The gas tube 705 and/or the rings 105 can be changedtogether. Either the gas tube 705 or the rings 105 can be changed alone(without changing the other). Thus, the gas tube 705 and the rings 105can be changed or used independently with respect to one another.

In operation, a shooter fires the firearm 700, 800 and hot, highpressure gas is provided by the cartridge. For an M16 or M4 type ofrifle, the gas travels through a front sight 4501 to the gas tube 705,then through the gas tube 705 and the bolt carrier key 752 to the boltcarrier 702, where the gas moves the bolt carrier 702, and consequentlythe bolt 100, so as to effect extraction of the spent cartridge andchambering of a new cartridge. The bolt 100 is disposed within a gascylinder 701 formed in the bolt carrier 702. During sustained fullyautomatic fire, the gas tube 705 is exposed to a substantial quantity ofhot gases from the fired cartridges. According to an embodiment, thethreads 707 provide increase surface area for radiating this heat sothat the temperature of the gas tube 705 can be maintained within anacceptable range.

Referring again to FIG. 9, as the gas tube 705 heats ups, it expandsboth in length and diameter. According to an embodiment, the length,Dimension M, of the gas tube 705 is sufficiently short so as toaccommodate thermal expansion of the gas tube 705 in length withoutcausing the firearm 700 to malfunction. Such malfunction can occur whenthe length, Dimension M, of the gas tube 705 is long enough such thatthermal expansion makes it too long and the rear end thereof impacts thecarrier key 752 when the firearm cycles. Such impacting of the gas tube705 can result in the gas tube 705 deforming and failing.

According to an embodiment, the diameter, Dimension N, of the gas tube705 is sufficiently small so as to accommodate thermal expansion of thegas tube 705 in diameter, particularly at the carrier key 752 interfacethereof, without causing the firearm 700 to malfunction. Suchmalfunction can occur when the diameter, Dimension N, of the gas tube705 is great enough such that thermal expansion makes it too tightwithin the carrier key 752 and the rear end thereof binds or freezesinstead of sliding within the carrier key 752. Such binding of the gastube 705 can result it the gas tube 705 deforming and failing. Therearward end of the gas tube 705 can be a bead 725.

FIG. 11 is a cross-sectional side view of a rearward end of the carrierkey 752 of FIG. 10. The rearward end or bead 725 of the gas tube 705 isreceived within the carrier key 752. When a contemporary gas tube 705expands in length, such as due to the heat of sustained fully automaticfire, it may bottom out or interfere within the carrier key 752, suchthat the gas tube 705 bends undesirably due to such expansion. Suchbottoming out and/or bending can inhibit uniform cycling or otherwiseprevent desired operation of the firearm 700.

According to an embodiment, the gas tube 705 can be shorter in length,Dimension M of FIG. 9, such that additional or desirable clearance,Dimension T of FIG. 11, is provided between the bead 725 and anyportions of the carrier key 752 that the bead 725 can bottom out orinterfere with during such expansion. Dimension T is partially definedby Dimension M, which is discussed further herein. Dimension M is sizedsuch that Dimension T does not decrease to zero as the firearm 700 heatsup. Dimension T can be 0.227-0.289 inch based on the maximum temperaturedifference between the M16 rifle's gas tube and barrel of 2380°F.×0.00000636 (Thermal Expansion Coefficient for Steel)×15 inch length(M)+0.062 tolerance.

According to an embodiment, the gas tube 705 can be shorter in length,Dimension M and the bead 725 can have a reduced diameter, Dimension N.Thus, undesirable interferences can be mitigated and uniformity ofcycling can be enhanced and a more reliable firearm can be provided.

FIG. 12 is a flow chart showing a method for making a firearm 700 havingthe gas tube 705, according to an embodiment. The method can comprisecutting a piece of 1/4 OD×0.065 wall, stainless steel tubing, forexample, to a desired length as shown in block 1101. For example, thetubing can be cut to a length of approximately 9.668 inches. The tubingcan be cut with a tubing cutter or a saw, for example.

The method can further comprise forming threads 707 upon the cut tubing,as indicated in block 1102. For example, 1/4-32 threads can be formedupon a section of tubing having a diameter of approximately 0.250 inch.The threads 707 can be formed with a lathe or with a die, for example.

The method can further comprise forming a first bend 711 in the tubing,as indicated in block 1103. A second bend 712 can be formed in thetubing, as indicated in block 1104 to define the gas tube 705. The firstbend 711 and the second bend 712 can be formed consecutively orsimultaneously. The first bend 711 and the second bend 712 can be formedusing a fixture, jig, or tubing bend, for example.

The gas tube 705 can be installed in a firearm 700 as indicated in block1105. For example, the gas tube 705 can be installed in an M16 or an M4type of firearm 700. The bead 725 can be formed on the reward end of thetube 705 to facilitate a desired fit into a gas block interface of thefirearm 700. The bead 725 can be formed at any desired point in thefabrication process. For example, the bead 725 can be formed eitherbefore or after the threads 707 are formed.

Referring again to FIG. 9, the gas tube 705 can comprise a gas tuberetention hole 751 that is used to pin (attach) the tube to the frontsight block 4501. According to an embodiment, the length, Dimension M,of the gas tube 705 from the center of the gas tube retention hole 751to the rear end of the gas tube 705 and/or the rear end diameter,dimension N, of the bead 725 can be approximately the same as for acontemporary gas tube 705 for an M16 and/or M4. For example, Dimension Mcan be approximately 9.600 inches for an M4 and can be approximately14.98 inches for an M16. For example, Dimension N can be approximately0.180 inch. Thus, in one or more embodiments the gas tube 705 canreadily replace the contemporary gas tube of an M16 and/or M4.

According to an embodiment, the length, Dimension M, and/or the rear enddiameter, Dimension N, of the bead 725 can be less than for acontemporary gas tube 705 for an M16 and/or M4. For example, Dimension Mcan be less than 9.570 inches for an M4 and can be less than 14.95inches for an M16. For example, Dimension N can be less than 0.1792 inchdiameter. Thus, the gas tube 705 can be approximately 0.100 inch shorterand can have an outer diameter of approximately 0.001 inch less at therear end, i.e. the bead 725, as compared to a standard gas tube 705 forthe same firearm 700. One or more embodiments can fit within the carrierkey 752 of an M16 and/or M4 and can readily replace contemporary gastubes 705. The shorter length, Dimension M, and the smaller outerdiameter, Dimension N, can better accommodate thermal expansion, such ascan be caused by using larger capacity magazines. Thus, the gas tube 705can have further enhanced heat resistance.

According to an embodiment, the outer diameter, Dimension Q, of aportion of the gas tube 705 at the rear end thereof can be approximately0.171 inch. The diameter, Dimension P, of the gas tube 705 can be 0.186inch.

The dimensions of the gas tube 705, as well as the configurationthereof, including any bends therein, can be whatever is necessary tofit a particular firearm. More or less than two bends can be used. Thus,the gas tube 705 can have any desired shape and configuration.

One or more embodiments can provide a replacement for contemporary gastubes 705. Such embodiments are less prone to overheating and lesslikely to malfunction due to heat induced weakness and/or heat inducedthermal expansion, particularly during sustained fully automatic fire ofthe firearm 700. Thus, the firearm 700 can cycle and fire more uniformlyand can be substantially more reliable.

One or more embodiments can provide a replacement for contemporary gastubes 705 that can withstand the heat of firing at least as well asother components of the firearm 700. Thus, a failure or problem with thegas tube will be substantially less likely to be the cause of amalfunction of the firearm 700.

An often neglected problem in gas operated firearms is gas port erosion.Gas port erosion causes the gas port to become larger, which allows moregas to be used and thus gradually speeds up the gun cycle. Speeding upthe gun cycle can cause feed jams, failures to extract, and carrierbounce misfires. It can also increase wear on the firearm and reduceaccuracy during use of the firearm.

The M4 carbine has more trouble with gas port erosion than the M16rifle, even though both of these firearms use the same bolt carriergroup. The M4's gas port location is closer to the chamber, where gasport erosion is more aggressive. Because of gas port erosion, the M4'sunlocking cam can begin to unlock too early in the firing cycle and thuscan cause a bolt with standard locking lugs to break at the lugs or campin hole. This typically does not occur in the M16 rifle and typicallydoes occur in new M4s. It generally only occurs in M4s that have firedenough to substantially erode the gas port. In addition to reliabilityproblems, the resulting high rate of fire makes the gun lesscontrollable on full auto, wastes ammunition, and intensifies heatproblems.

Contemporary M16/M4 firearms have a gas tube 705 with a plug 706 (FIG.40) at the front end of the gas tube 705. However, the plug 706 of acontemporary M16/M4 firearm does not substantially restrict gas flow.Contemporary M16/M4 firearms rely upon the gas port 1003 formed in thebarrel to perform a gas metering function. The gas port 1003 is subjectto erosion as discussed herein and thus suffers from substantialdisadvantages with regard to this metering function.

More particularly, the M16 and M4 use the gas port 1003 diameter as themeans to control the amount of gas flow. However, the forward corner ofthe gas port 1003 intersection with barrel bore is eroded from itsoriginal sharp corner into an enlarging triangle by the scrubbing ofeach passing bullet and the bombardment of propellant grains. Thiserosion of the gas port 1003 increases its size and thus undesirablyallows the gas flow therethrough to increase over time. As the gas flowincreases, the gun cycle speeds up, undesirably resulting in feed jams,extraction failures, and/or carrier bounce. Misfires begin and growworse over time until the gun cripples itself from excessively wornand/or broken parts.

As shown in FIG. 10B, a gas metering plug 1001 can be installed in thefront end of the gas tube 705 to mitigate the undesirable effects of gasport erosion. The gas metering plug 1001 can have a gas metering hole1002 that the gas from the barrel must flow through before entering thegas tube 705. According to an embodiment, the gas metering hole 1002 isout of reach of bullet scrubbing and the impact of propellant grains.The gas metering plug 1001 can be made of a heat resistant material, sothat it remains substantially unchanged by any amount of firing.

According to an embodiment, the gas metering hole 1002 is alwayssmaller, e.g., has a smaller diameter, than the hole of the gas port1003 (such that the gas metering hole 1002 always performs a gasmetering function). Thus, although the gas port 1003 continues to erodeso that the gas flow that reaches the gas metering hole 1002 continuesto increase in pressure, the gas metering hole 1002 meters the gas andthus mitigates the undesirable effects of gas port erosion so as to theextend the useful life of the gun.

As discussed herein, the M16 service rifle and the M4 carbine have avariety of reliability shortcomings. Undesirable forward and rearwardbouncing of the bolt carrier 702 is one such shortcoming. Insufficientdwell and early unlocking of the bolt 100 are another shortcoming.Methods and systems disclosed herein can be used in combination with oneanother to mitigate shortcomings of the M16/M4. For example, a drop inreplacement kit can be provided to address this and others of theseshortcomings.

FIGS. 13A and 14 show a bolt carrier 702 having a longer dwell, doublecut cam 1301 (FIG. 33B) and an anti-bounce assembly 1305, according toan embodiment. The double cut cam 1301 is particularly useful whenapplied to the M4 due to the insufficient dwell of the M4. To preventbroken bolts, the double cut cam 1301 can have a 0.062 longer dwell(e.g., an overall dwell of approximately 0.132 inch) as compared to thestandard M4 cam. Thus, the bolt 100 can be delayed substantially beforethe unlocking cam surface 3301 (FIG. 33B) begins to rotate the bolt 100to its unlocked position. This longer dwell at least partiallycompensates for the time differences between the M16 unlocking start andthe early start of the M4 due to its rearward gas port location, asdiscussed herein. The force on the extended bolt locking lugs 3601(FIG. 1) that would cause the extended bolt locking lugs 3601 to bind isthus reduced to the same resistance as in the M16 rifle, so that thecause of broken bolts is substantially eliminated.

However, if care is not taken, the longer locking dwell and longer cammay be a hindrance in that it defeats one of the features of the M4/M16bolt carrier assembly's design. When the bolt is in the most forward(unlocked) position relative to the bolt carrier, the extractor pin forthe extractor that also retains the extractor is trapped by the boltcarrier body. If the extractor pin is not trapped at all times by thebolt carrier body, it may result in a gun stoppage if the pin movestowards disengaging with the extractor and bolt.

Therefore, in one or more embodiments of the present disclosure, astepped extractor pin 1302/1312 is used to insure retention of theextractor pin as shown in FIGS. 13B-13E. The stepped pin 1302/1312, incombination with the extractor spring and extractor, form a springloaded detent to secure the pin rather than relying on the pin beingtrapped inside the bore of the bolt carrier.

FIG. 13B illustrates a detent feature which traps pin 1302. Steppedextractor pin 1302 may have opposing ends 1304 that are radiallyelevated about the longitudinally traversing center portion 1306 of pin1302. Elevated ends 1304 may be adjoined to center portion 1306 viaradial steps 1310. End portions 1304 may have beveled edges, such asfaces 1308, on either side of the elevated area.

FIG. 13C shows a bolt assembly cross section through an extractor pinhole (e.g., section is rotated 67.5 degrees to show the extractor on thetop and only shows features at the cross section). Pin 1302 may bedisposed in pin hole 1322 in bolt 100. Pin 1302 may be disposed withinhole 1322 and hole 1326 to prevent extractor 1324 from separating frombolt 100. Edges 1310 may engage with corresponding steps 1303. As shown,the extractor pin includes first and second ends and a central portionthat extends between the first and second ends, where the first andsecond ends have a common diameter, wherein the central portion has adiameter, and wherein the common diameter of the first and second endsis larger than the diameter of the central portion. In thisconfiguration, the extractor and the extractor pin cooperate to providea force on the extractor pin that misaligns the extractor pin with ahole in the extractor. For example, the extractor spring force pushesextractor 1324 outward so that edges 1310 of end portions 1304 abutcorresponding surfaces of an inner portion 1330 of the extractor that ispressed against smaller center portion 1306, thus, misaligning pin 1302with hole 1326 in the extractor and preventing pin 1302 from passingcompletely through extractor pin hole 1326 and resulting in disassembly.Pin 1302 may be removed by using a punch or by pressing the extractorinward until the diameters are aligned

In another embodiment of the present disclosure, as shown in FIG. 13D,stepped extractor pin 1312 may have a center portion 1316 that iselevated radially relative to end portions 1314. As shown, extractor pin1312 includes first and second ends and a central portion that extendsbetween the first and second ends, where the first and second ends havea common diameter, wherein the central portion has a diameter, andwherein the common diameter of the first and second ends is smaller thanthe diameter of the central portion. In this configuration, theextractor and the extractor pin cooperate to provide a force on theextractor pin that misaligns the extractor pin with a hole in the bolt.For example, the extractor spring force pushes extractor 1324 outward sothat the larger diameter of center portion 1316 is misaligned with boltpin hole 1322, thus, steps 1320 engage with corresponding surfaces 1307of the bolt preventing pin 1312 from passing completely through hole1322 and resulting in disassembly. Pin 1312 may be removed by using apunch or by pressing the extractor inward until the diameters arealigned.

FIG. 13E shows a bolt carrier assembly with a stepped extractor pin thatis not trapped by the bolt carrier body because the bolt has extended toa position at which opening 1322, in which the pin is disposed, isoutside the body of bolt carrier 702. In the arrangement of FIG. 13E,the stepped features of the extractor pin may prevent the extractor pinfrom disengaging and falling out of hole 1322.

A single cut cam of the same new length with 0.062 longer dwell wouldhave the same timing advantage, but the double cut has two additionaladvantages. The helix portion 3102 (FIG. 33B) of the cam has widerclearance for dust and dirt. Although the unlocking cam surface 3301 has0.062 longer time dwell, the cam pin and bolt head location on thelocking side have the same starting location as the standard cam so thatthe bolt head overtravels beyond the bolt holdopen device by the sameamount giving the holdopen enough time to rise into position.

According to an embodiment, the adverse effects of gas port erosion andhigher rate of fire (excessive cycle speed) can be substantiallymitigated by three compatible but separate features. First, a gasmetering plug 1001 can be installed in the end of the gas tube 705 andthe gas metering plug 1001 can have a gas metering hole 1002 that thegas must flow through.

Second, undesirable bounce of the bolt carrier 702 can be substantiallymitigated. It is not surprising that gas port erosion speeds up thefirearm cycle, because the bolt group (comprising the bolt 100 andrelated components) is thrown more vigorously to the rear. However, itis important to also appreciate that the forward cycle of the bolt groupalso undesirably speeds up. Faster forward movement is caused bybouncing of the bolt carrier 702 as the buffer 3503 (FIG. 35) and thebolt carrier 702 impact the rear wall 3577 of the firearm 700. Thebuffer 3503 doesn't bounce, but bolt carrier 702 does bounce. If rearbouncing of the bolt carrier 702 can be eliminated, then approximatelyhalf the rate of fire gain can be desirably eliminated.

For example, assume that the cyclic rate of fire of a new M4 is 800shots per minute and that the firearm has fired enough rounds to erodethe gas port sufficiently to speed up the cyclic rate to 1000 shots perminute. This represents an increase of 200 shots per minute in thecyclic rate. If that increase were cut in half, the gain would only be100 shots per minute. Thus, the firearm would have a cyclic rate of 900shots per minute instead of 1000 shots per minute and the useful life ofthe firearm would be substantially extended.

When the bolt group begins to move forward slowly, it starts to push thetop cartridge in the magazine forward, so that the top cartridge entersthe feed ramp at a slow speed and is smoothly cammed upward into thechamber opening. By way of contrast, if the bolt group bounces forwardat high speed, then the bullet point hits the feed ramp (which is 7°steeper in the M4 than in the M16) at high speed. The bullet tends tobounce higher as the cyclic rate increase. When the cyclic rateincreases sufficiently, the bullet will miss the chamber opening andjams the firearm 700. Although this commonly occurs with contemporary30-shot magazines, high capacity magazine provided by SureFire, LLC ofFountain Valley, Calif. are designed to feed reliably at a very widerange of cyclic rates.

Referring to FIGS. 13A-33A, a combination rate reducer and anti-bounceassembly, referred to herein as anti-bounce assembly 1305, can bemounted in the rear tubular section 1350 that is common to both the M16and M4 bolt carrier 702, according to an embodiment. The onlymodification needed to be made to the bolt carrier 702 is a vertical cutor slot 1352 formed through the left side wall of the bolt carrier 702as shown in FIG. 18.

As shown in FIGS. 15-17, the anti-bounce assembly 1305 can comprise asteel cylinder or anti-bounce weight 1400 having a first cavity 1511 andsecond cavity 1512 formed therein. A first spring 1521 can be disposedin the first cavity 1511 upon a first plunger 1531 and a second spring1522 can be disposed in the second cavity 1512 upon a second plunger1532. The first plunger 1531 and the second plunger 1532 can besubstantially hollow. A spring pin 1355 can interconnect the firstplunger 1531 and the second plunger 1532 and can pass through an opening1862 in an anvil 1351.

The anti-bounce weight 1400 can be free to slide within the bolt carrier702 and can be biased centrally by the first spring 1521 and the secondspring 1522, which can bear upon the anvil 1351. The anvil 1351 can befixed with respect to the bolt carrier 702. The anvil 1351 can bereceived within the slot 1352 formed in the bolt carrier 702. The firstcavity 1511 and the second cavity 1512 can have a first blockingshoulder 1541 and a second blocking shoulder 1542 that prevent the firstplunger 1531 and the second plunger 1532 from moving beyond theircentering positions, so that when inertia moves the anti-bounce weight1400 beyond center, then one plunger 1531, 1532 compresses itsassociated spring 1521, 1522 so as to provide a force that tends toreturn the anti-bounce weight 1400 to center while the other plunger1532, 1531 and spring 1522, 1521 are blocked from acting upon theanti-bounce weight 1400.

As shown in FIG. 15, the anti-bounce weight 1400 is in a zero ornon-impact position. This is the position of the anti-bounce weight 1400prior to firing the firearm 700 and after the firearm 700 has completeda firing cycle.

As shown in FIG. 16, the anti-bounce weight 1400 is in a rearwardimpact. This is the position of the anti-bounce weight 1400 after firingthe firearm 700 once the bolt carrier 702 has moved rearwardlysufficiently to cause the anti-bounce weight 1400 contact the anvil1351. The anvil 1351 has traveled rearward with the bolt carrier 702 tocause the impact.

As shown in FIG. 17, the anti-bounce weight 1400 is in a forward impact.This is the position of the anti-bounce weight 1400 after firing thefirearm 700 once the bolt carrier 702 has ceased moving rearwardly tocause the anti-bounce weight 1400 to again contact the anvil 1351 on theopposite side of the anvil 1351 with respect to that shown in FIG. 16.The anvil 1351 has traveled forward with the bolt carrier 702 to causethe impact.

As shown in FIG. 18, a central cavity 1801 can be formed between the twocavities 1511 and 1512 of the anti-bounce weight. The central cavity1801 can define a continuous passage between the two cavities 1501 and1502. The anvil 1351 is disposed within the central cavity 1801. Theanvil 1351 moves within the central cavity 1801 as the bolt carrier 702travels rearward and forward.

The two plungers 1531 and 1532 can extend through corresponding openings1821 and 1822 into the central cavity 1801. The anti-bounce assembly1305 can be secured within the bolt carrier 702 by inserting theanti-bounce assembly 1305 into the tubular section 1350 of the boltcarrier 702, then placing the anvil 1351 into the slot 1352 in the boltcarrier 702 and on into the central cavity 1801, and then inserting thespring pin 1355 through the hollow plungers 1531, 1532 and through thehole 1862 in the anvil 1351.

The anti-bounce weight 1400 can slide forward and rearward within thetubular portion 1350 of the bolt carrier 702. The springs 1521 and 1522can tend to center the anti-bounce weight 1400. The dimensions of thecentral cavity 1801 can allow the anti-bounce weight 1400 to move foreand aft approximately 0.10 inches, for example, before the anti-bounceweight 1400 impacts the anvil 1351. Such motion is resisted in eitherdirection by the force of each spring 1521, 1522 and by the fact thateach plunger 1531, 1532 has a travel limiting stop or blocking shoulder1541 (FIG. 19) formed thereon. Thus, when inertia drives the anti-bounceweight 1400 forward to strike the anvil 1351, then only the rearwardspring 1522 is compressed (as shown in FIG. 17), while the forwardspring 1521 and plunger 1531 move away from the anvil 1351 and theopposite occurs when the weight 1400 move rearward (as shown in FIG.16). In this way, the springs 1521 and 1522 are preloaded and biased tohold the anti-bounce weight 1400 in mid position, e.g., approximatelycentered (as shown in FIG. 15) within its limits of travel.

When the bolt carrier 702 impacts forward and tends to bounce rearward,the anti-bounce weight 1400 impacts forward again (as shown in FIG. 17)and vice-versa (as shown in FIG. 16). Thus, the anti-bounce weight 1400partially defines an anti-bounce device in both directions, not just inthe forward direction. Since the anti-bounce assembly 1305 mitigatesrearward bounce, it is also a rate reducer (it tends to reduce thecyclic rate of a firearm). According to one or more embodiments, theanti-bounce assembly 1305 can be a semi-permanent installation. That is,the anti-bounce assembly 1305 can be removed by driving the spring pin1355 into the forward plunger 1532 or the anti-bounce assembly 1305 canremain in place since standard disassembly of the firing pin, cam pin,and bolt can be performed with the device installed.

FIGS. 19-23 show further detail regarding the construction of theanti-bounce assembly 1305. The anvil 1351 is removed from FIGS. 19-22for clarity. The anvil 1351 is shown in FIG. 23 positioned for insertioninto slot 1352 formed in the bolt carrier 702. The anvil 1351 bothmaintains desired positioning of the anti-bounce weight 1400 within thebolt carrier 702 and provides a stop for defining the limits of motionof the anti-bounce weight 1400. The anti-bounce weight 1400 strikes theanvil 1351 as the anti-bounce weight 1400 functions to mitigateundesirable bouncing of the bolt carrier 702.

FIG. 24 shows a cross section of the modified bolt carrier 702. Thecross section is taken where the slot 1352 is formed to receive theanvil 1351.

FIG. 25 and FIGS. 31A-31C show the anvil 1351. The anvil 1351 can begenerally crescent shaped with a hole 1862 proximate the middle thereof.The anvil can have a curved outer surface 1362 which can conformgenerally to the curvature of the bolt carrier 702 within which theanvil 1351 is disposed. The anvil 1351 can have any desired shape. Thehole 1862 receives the spring pin 1355.

FIG. 26 shows an impact area 1370 where the anti-bounce weight 1400strikes the bolt carrier 702 curing cycling of the firearm 700. Abearing surface 1371 of the bolt carrier 702 where the anvil contactsthe bolt carrier 702 when the anvil is installed in the bolt carrier 702is also shown.

FIG. 27 shows a cross section of the bolt carrier 1350 with the anvil1351 installed in the slot 1352. The spring pin 1355 is installed in theplungers 1531 and 1532.

FIGS. 28A and 28B show the anti-bounce assembly 1305 in cross section.The anti-bounce weight 1400, the plungers 1531 and 1532, the springs1521 and 1522, the anvil 1351, and the spring pin 1355 are installed inthe bolt carrier 702.

FIGS. 29A-29C show the cavities 1511 and 1512 of the anti-bounce weight1400 where the plungers 1531 and 1532 are disposed. The plungers 1531and 1532 are removed for clarity.

FIGS. 30A-30D show a plunger 1531, 1532. The plunger 1531, 1532comprises a generally cylindrical shaft or spring guide 1535 upon whichthe spring 1521, 1522 is compressibly disposed and a shoulder 1536against which the spring 1531, 1532 bears. A limiting stop 1541partially defines the limit of travel of the anti-bounce weight 1400, asdiscussed herein. FIG. 31A-31C show the anvil 1351. FIG. 31B is a sideview of the anvil 1351. FIG. 31C shows a cross-section of the anvilthrough the hole 1862.

FIGS. 32A-32F are various views showing a modification of the boltcarrier 702, according to an embodiment. The slot 1352 can be cut into astandard bolt carrier 702 to receive the anvil 1351. The slot 1352 canbe milled into the bolt carrier 702, for example. The anti-bounceassembly 1305 can thus be easily added to a standard bolt carrier 702.

FIGS. 33A-33B show a longer dwell, double cut cam 1301, according to anembodiment. Exemplary dimensions for the double cut cam 1301 areprovided. Double cutting the cam 1301 delays unlocking of the bolt 100and provides other advantages, as discussed herein.

The longer dwell of the double cut cam 1301 allows the chamber pressureto drop more that is allowed by the single cut cam of a standard M4carbine, so as to better assure that the pressure is low enough tosafely and reliably disengage the extended bolt locking lugs 3601. Theanti-bounce weight makes the firearm 700 more controllable and reducesthe cyclic rate as compared to a standard M16/M4.

Double cutting the cam 1301 extends the bolt head 3530 (FIG. 36A)approximately 0.062 inch forward. This extended amount adds 0.130 inchof additional length to the extended bolt locking lugs 3601 for anadditional total extension of approximately 0.192 inch out of the frontof the bolt carrier 702 compared to standard M16/M4. In the standardM16/M4 firearm 700 (FIG. 35), such double cutting of the cam 1301 andsuch extended bolt locking lugs 3601 eliminates the 0.188 nominal overtravel of the bolt head 3530 beyond the bolt catch 3654 and thus blocksproper functioning of the bolt catch 3654 (FIG. 35).

A bolt group 3650 can include the bolt 3610, the bolt carrier 702, andthe carrier key 752, among other items. To facilitate proper functioningof the bolt catch 3654 and to improve on such functioning withoutundesirably mitigating the benefits of the more robust extended boltlocking lugs 3601, as well as the delayed unlocking that results fromthe extended bolt locking lugs 3601 and the double cut cam 1301, ashortened buffer 3503 and modified carrier key 752 allow the bolt group3650 to travel approximately an additional 0.360 inch rearward.

With particular reference to FIG. 33B, examples of dimension areprovided for the double cut cam 1301. These dimensions provided thelonger dwell. Other dimensions can similarly provide a longer dwell.

The helix portion 3102 of the double cut cam 1301 can provide widerclearance to better accommodate soiling, e.g., dust and dirt. Theunlocking cam surface 3301 can have 0.062 longer time dwell. The cam pinand bolt head location (not shown) on the locking side can have the samestarting location as the standard cam so that the bolt head overtravelsbeyond the bolt holdopen device by the same amount giving the boltholdopen device sufficient time to rise into position.

Referring now to FIGS. 34A-34P, the carrier key 752 can have a reducedprofile that avoids interference, e.g., impacting of the carrier key 752with a lower receiver's rear band 3640 (FIG. 36A). The reduced profileof the carrier key 752 can be necessitated by the longer extended boltlugs 3601. For example, the carrier key may be shortened byapproximately 0.400 inch to facilitate an increased stroke.

The carrier key 752 can have a single bolt hole 3421, as opposed to acontemporary carrier key which has two bolt holes. It has been foundthat the use of a single mounting bolt is sufficient for securelyattaching the carrier key 752 to the bolt carrier 702 and the use of asingle mounting bolt facilitates increase travel of the bolt carrier 702due to the use of the longer extended bolt locking lugs 3601, asdiscussed herein. The use of a single mounting bolt facilitatesadditional clearance to define low profile 3422 to prevent the rearportion of the carrier key 752 from contacting the receiver's rear band3640 when the firearm 700 cycles. Further, the carrier key 752 can bemounted in a deeper cut channel of the bolt carrier 702.

The use of a 0.500 inch shorter carrier key 752, a shortened buffer 3503(FIG. 36A) can increase the bolt carrier 702 allowable travel byapproximately 13% and can reduce the rate of fire of the firearm 700 toabout 80% of what it otherwise is. Except for the design of the key 752,the only change to the carrier 702 can be that two number 8 screw holesare replaced with a single 10-32 screw hole.

Although this alone does not necessarily reduce parts wear, it canincrease full auto controllability and hit probability, conserveammunition and reduce heat buildup. Thus, operation and reliability canbe enhanced. The use of such a carrier key 752 can comply and worknormally without the shortened buffer 3503 (FIG. 36A). It can thereforebe offered to create the option to use a shortened buffer and springstack for a reduced rate of fire.

The carrier key 752 is shown during various manufacturing steps thereof.More particularly, FIGS. 34A-34C show a block shape of the carrier key752. FIGS. 34D-34G show the carrier key 752 after a drill and reamprocesses. FIGS. 34H-34J show the carrier key 752 after lath turning.FIGS. 34K-34N show the carrier key 752 after form cutting. FIGS. 34O-34Pshow the profile of the finished carrier key 752.

According to an embodiment, more robust extended bolt locking lugs 3601can be formed upon the bolt and more robust extended barrel locking lugs4410 can be formed upon the barrel extension 3612, as discussed herein.The use of more robust extended bolt locking lugs 3601 and more robustextended barrel locking lugs 4410 mitigates failure thereof. Suchfailure of the extended bolt locking lugs 3601 and the extended barrellocking lugs 4410 can result in damage to the firearm 700, as well aspossibly lose of life, particularly in police use and battlefieldoperations.

It has been determined that extended locking lugs used in combinationwith a barrel extension in a firearm, such as an M4 carbine, and alonger, less steep feed ramp than the standard M4 feed ramp reducedbullet bounce off of the feed ramp. However, the longer locking lugs ofboth the bolt and/or barrel extension, whether only one is lengthened orboth are lengthened, may create a similar dilemma as the longer cam(e.g., the extractor pin becomes exposed) as discussed above inconnection with FIG. 13A. If care is not taken, whether used with thelonger cam or with a standard M4 cam, the longer locking lugs overcomethe extractor pin retention feature of being trapped within the boltcarrier body. A stepped pin such as stepped pin 1302/1312 in combinationwith the extractor spring and extractor forms a spring loaded detent tosecure the extractor pin rather than trap the pin inside the bore of thebolt carrier as described above that becomes particularly beneficialwhen using the extended bolt locking lugs, extended barrel extensionlugs, or the longer cam whether used individually or in combination witheach other.

For example, a barrel extension for use in a firearm (e.g., M4 carbine)with extended locking lugs, which require a lengthened bolt such thatwhen the bolt relative to the bolt carrier is in its most forwardunlocked position the bolt's extractor pin is fully exposed and notretained by the bolt carrier (see, e.g., FIG. 13E), the extractor pin isstepped so that in combination with the bolt's extractor spring andextractor acts as a detent to retain the extractor pin as shown in, forexample, FIGS. 13B-D.

As shown in FIGS. 36B-L, in various embodiments, a bolt carrier assemblyfor use in an M4 carbine may have a bolt with extended locking lugs, andthe lengthened bolt is such that when the bolt relative to the boltcarrier is in its most forward, unlocked position the bolt's extractorpin is fully exposed and not retained by the bolt carrier. The extractorpin is thus stepped and, in combination with the bolt's extractor springand extractor, acts as a detent to retain the extractor pin.

In an embodiment of the present disclosure, bolt 100 may have extendedlocking lugs 3601 (e.g., extended locking lugs having a length ofapproximately 0.335 inches). Bolt 100 may have pin hole 1322 to receivea stepped pin such as one of stepped pin 1302 or stepped pin 1312described herein. As shown in FIGS. 36M-36P, extractor 1324 may bedisposed in a slot 3606 of bolt 100 and secured by a stepped pin andforce provided by extractor spring 3602.

In another embodiment of the present disclosure, as shown in FIG.36U-36Y, a bolt carrier 702 with a shortened key 3604 for increasedtravel may be included to maintain the M4's original bolt catch overtravel. The limit of increased bolt group travel is reached atapproximately 0.156 inch before the bottom front chamfer of the boltcarrier 702 over travels the notch 3632 in semi auto hammers. Theapproximate 2.85 inch length of the buffer 3503 prevents this overtravel.

An approximately 0.188 inch standard over travel of the bolt head 3530with respect to the bolt catch 3654 provides sufficient time to operatethe bolt catch 3654, unless the cyclic rate of the firearm 700increases. The cyclic rate can increase due to gas port erosion or theuse of a sound suppressor. According to an embodiment, the over travelis increased to approximately 0.355 inch for greater reliability.

The additional approximately 0.360 inch bolt group travel reduces therate of fire (cyclic rate) and increases the reliability of the firearm700. The anti-bounce assembly, gas metering tube, and improved gas tubediscussed herein also increase the reliability of the firearm 700.

FIG. 35 is a cross-sectional side view of a portion of a standard M16/M45.56 mm firearm 7000. The bolt locking lugs 3501, the carrier key 752,the buffer 3503, the cam 1301, the ramps 3505, the bolt 100, the barrelextension 3612, and the bolt carrier 702 are standard (contemporary).That is, the firearm 700 has not been modified according an embodiment.The carrier key 752 has two screws 3571 that provide attachment of thecarrier key 752 to the bolt carrier 702. FIG. 35 is provided to betterfacilitate a contrast with respect to embodiments described herein.

FIG. 36A is a cross-sectional side view of a portion of an M16/M4 5.56mm and 6.8 mm firearm 700, according to an embodiment. FIG. 36A showsthe use of the buffer 3503 that is 0.360 inch shorter than standard, theuse of the carrier key 752 that is mounted via a single screw 3671 in adeeper cut carrier channel to facilitate the use of the anti-bounceassembly 1305.

The bolt carriers 702 in both FIG. 35 and FIG. 36A are shown in both theforwardmost (locked) and rearwardmost positions. These are the twoextremes of travel for the bolt carrier 702.

The extended bolt locking lugs 3601, carrier key 752, buffer 3503, cam1301, and ramps 3505 have been modified to provide more robust operationof the firearm 700. More particularly, a bolt 3610 having more robustextended bolt locking lugs 3601 and a barrel extension 3512 having morerobust extended barrel locking lugs 4410. For example, the extended boltlocking lugs 3601 can be lengthened so as to provide at leastapproximately 1.3 times (such as approximately 1.35 times) the sheararea as compared to those of the standard M16/M4 firearm (FIG. 35).

FIG. 37A is an enlarged cross-sectional side view showing the unmodifiedor standard bolt locking lugs 3501 of the standard M16/M4 5.56 mmfirearm in the upper portion of the figure and showing the more robustextended bolt locking lugs 3601 of the M16/M4 5.56 mm and 6.8 mmfirearm, according to an embodiment, in the lower portion of the figure.The standard bolt locking lugs 3501 and the more robust extended boltlocking lugs 3601 are shown engaged with the complementary standardbarrel extension locking lugs 3511 and the more robust extended barrellocking lugs 4410, respectively.

As shown in FIGS. 37A and 37B, a flange 3613 can be formed upon thebarrel extension 3612 such that the flange 3613 is approximately 0.130inch from a forward end of the barrel extension 3612. Thus, instead ofthe flange 3613 of an embodiment being at the forward end of the barrelextension 3612, as is the flange 3513 of a standard M16, the flange 3613is rearward of the forward end of the barrel extension 3612 by an amountapproximately equal to the added length of the bolt lugs 3601 and thebarrel extension lugs 4410. In this manner, the threaded length of thebarrel is maintained and the strength of the barrel is not compromised.This is done without requiring any change to the receiver body, thebarrel nut, the fore end of the firearm, or the position of the gasblock.

FIG. 38 shows the feed ramps 3505 and standard barrel locking lugs 3511of the standard M16/M4 5.56 mm firearm 700. The feed ramps 3505 areformed in the barrel extension 3512. The narrower, steeper feed ramps3505 decrease the reliability of the firearm 700 by allowing bullets tobounce high and occasionally miss the chamber, thus causing a feed jam.

FIG. 39 is an end view showing the feed ramps 3605 and extended barrellocking lugs 4410 for an M16/M4 5.56 mm and 6.8 mm firearm 700,according to an embodiment. The feed ramps 3605 are formed in the barrelextension 3612. The stronger extended barrel locking lugs 4410 and thewider and longer (less steep) feed ramps 3605 facilitate more reliableoperation of the firearm 700. The wider and longer feed ramps 3505provide a better feed angle for the firearm 700 and are thus less likelyto cause a jam. Examples of parameters used to define the wider andlonger feed ramps 3505 are shown. For example, the length of the barrelextension locking lugs and feed ramps may be approximately 0.289 inchand the steepness may range from approximately 37 degrees to 45 degreesto reduce bullet bounce off the feed ramps (e.g., a ramp steepness of37.5 degrees rather the 45-degree ramp steepness of an M16 firearm or52-degree ramp steepness for an M4 firearm).

Referring now to FIGS. 40-44, a rearwardly positioned gas port 1003 of acontemporary M16/M4 type of firearm 700 can be moved forward, away fromthe receiver, so as to increase the time between firing a cartridge andcycling the bolt of the firearm and so as to reduce the pressure used tocycle the firearm 700. The cyclic rate of the firearm 700 can be reducedand stress on components of the firearm 700 can be reduced. In thismanner the reliability of the firearm 700 can be substantially enhanced,as discussed herein.

FIGS. 40 and 41 show the rearwardly positioned gas port 1003 as it ispositioned in a contemporary M4 firearm. FIG. 41 additionally shows theuse of the gas metering plug 1001, according to an embodiment. FIGS.42-44 show the gas port 1003 moved forward as well as showing the use ofthe gas metering plug 1001, according to an embodiment.

With particular reference to FIG. 40, the front sight block (also knowas a gas block or forging) 4501 and gas tube 705 of a contemporaryfirearm 700, i.e. an M4 carbine, are shown. Firearms of the M16/M4family are constructed such that the rearwardly positioned gas port 1003of the barrel 4507 is located proximate the rear band 4504 of the sightblock 4501. Gas from the barrel 4507 passes through the rearwardlypositioned gas port 1003 and through a gas passage 4503 in the rear band4504 to reach the gas tube 705. The gas port 1003 performs the gasmetering function and is subject to wear, thus causing problems asdiscussed herein.

With particular reference to FIG. 41, the gas port 1003 is again locatedproximate the rear band 4504 of the sight block 4501. The gas meteringplug 1001 has been added to the gas tube 705 to regulate the flow of gasfrom the gas port 1003 to the gas cylinder 701 (FIG. 7), to compensatefor wear of the gas port 1003 as discussed herein. Thus, the gasmetering plug 1001can be installed in a firearm 700 that has the gasport 1003 in the standard location, i.e. proximate the rear band 4504.

A thick wall gas tube 705 can additionally be used, according to anembodiment. The gas metering plug 1001 can be disposed within the frontsight block 4501, such as within that portion of the thick wall gas tube705 that is received within the front sight block 4501. The gas meteringplug 1001 can be installed anywhere along the path of the gas from thegas port 1003 to the gas cylinder 701 as long as the gas metering plug1001 is installed sufficiently far away from the gas port 1003 so as tonot be substantially subject to wear cause by the hot gases and burningpropellant.

With particular reference to FIGS. 42-44, a gas passage 4702 can beformed in the front band 4505 of the sight block 4501. Moving the gaspassage 4702 to the front band 4505 allows the gas port 1003 to be movedforward in the barrel 4507, thus delaying the time at which the gas actsupon the piston 101 (FIG. 1) and decreasing the pressure of the gas. Inthis manner, the cyclic rate of the firearm 700 can be reduced andundesirable forces acting upon components of the firearm 700 can bereduced.

The gas port 1003 can be re-located to this more forward positionwithout moving or changing the shape of the front sight block 4501 orthe rear 4504 and front 4505 bands, which surround the barrel 4507 toattach the front sight block 4501 to the barrel 4507. The gas passage4702 is drilled in the front band 4505 instead of in the rear band 4504.Clearance 4810 can be provided in the lower portion of the front band4505 either prior to such drilling or by the drilling process itself soas to facilitate such drilling.

The rear band 4504 and the front band 4505 can be formed integrally withthe front sight block 4501 (as a single forging or casting, forexample). Alternatively, the rear band 4504 and the front band 4505 canbe formed separately with respect to the front sight block 4501.

The gas port 1003 (FIG. 40) of a contemporary firearm was originallylocated in the rear band 4504 when the front sight block 4501 wasdesigned for the longer barrel of the M16 rifle. Then, the same frontsight block 4501 and the rearwardly positioned gas port 1003configuration was used for the 5½ inch shorter carbine barrel. In thecarbine, the front sight block 4501 was moved rearward 5½ inches (withrespect to the rifle) to maintain the standard distance from the bayonetlug to the muzzle. The rearwardly positioned gas port 1003 was alsomoved rearward 5½ inches.

The distance from bullet start (firing) to the gas port determines theavailable pressure and the distance from gas port to the muzzledetermines the time that pressure is available, thus the ratio betweenthe two distances determines the impulse (force multiplied by time) ofthe gas system for the gun. The ratio for an 18½ inch bullet travellength of the rifle barrel is 63/37 (63% from the bullet start to thegas port and 37% from the gas port to the muzzle). The ratio for the 13inch bullet travel length of the carbine barrel is 47/53. Since theratio used for the rifle barrel proved to be reliable over decades ofservice, this reliability suggests that the distance from bullet startto the gas port used on the carbine barrel is two inches shorter thannecessary to maintain the same ratio as the rifle. It thus indicatesthat the gas port is much closer to the firing chamber (bullet startposition) in contemporary M16/M4 firearms than it needs to be.

Placing the gas port 1003 closer to the chamber causes the gas port 1003(FIG. 46) to be subjected to higher pressure and temperature thannecessary. This is because the closer the gas port 1003 is to thechamber, the higher the temperature and pressure to which the gas port1003 is exposed. Higher temperatures and pressures undesirably causemore aggressive gas port erosion. Additionally, as the carbine's gassystem starts unlocking the bolt while there is higher pressure in thechamber (compared to the rifle), the bolt's cam pin hole and standardbolt locking lugs 3501 are undesirably subjected to more stress, whichcan cause them wear prematurely, bind, and ultimately fail.

Without changing the external dimensions of the front sight block 4501(these dimensions need to remain the same to accommodate the bayonet,tripod, barrel launched grenade and separate grenade launcher) a fulltwo inch correction isn't feasible. However, it is feasible toreposition the gas port 1.23 inches further forward as discussed herein,thus gaining substantial benefit. Thus, by moving the barrel's gas portand the gas block's passageway hole from the rear band 1.23 inchesforward into the front band 4505, problems associated with contemporaryfirearms can be substantially mitigated.

A bore 4712 can be formed in the front sight block 4501 for receivingthe gas tube 705. The bore 4712 can extend completely through the frontsight block 4501.

As best shown in FIGS. 43 and 44, the gas metering plug 1001 cancomprise a bore or gas metering hole 1002 and an inlet 4804. The inlet4804 and/or gas metering hole 1002 are sized and configured to providethe desire gas metering function. That is, either the inlet 4804, gasmetering hole 1002, or both are configured to allow a desired amount ofgas to flow from the gas port 1003 to the gas tube 705. The inlet 4804and/or gas metering hole 1002 can define a fixed, calibrated orifice fordetermining the amount of gas flow through the gas metering plug 1001.Thus, the amount of gas used to cycle the firearm can be bettercontrolled, e.g., can be fine tuned.

An opening 4803 can be formed in the gas tube 4791 to facilitate gasflow from the gas passage 4702 to the gas metering plug 1001. A hole4802 can be provided through the gas metering plug 1001 and/or the gastube 705 to facilitate attachment, e.g., pinning, of the gas tube 705and/or the gas metering plug 1001 to the front sight block 4501.

FIG. 45 shows the anti-bounce weight 1400 having a chamfer 5101 formedthereon to provide clearance for the hammer of the firearm 700,according to an embodiment. According to other embodiments, the chamfer5101 can be omitted, such a when the anti-bounce weight 1400 will notinterferer with desired movement of the hammer.

FIG. 46 shows a cam pin 5200 having a chamfer 5201 formed thereon toprovide clearance for the cam 1301, according to an embodiment. Thechamfer 5201 can extend around the periphery of the end of the camp pin5200 that extends into the cam 1301. The chamfer 5201 can be omitted inembodiments where tolerances permit.

One or more embodiments can be used in various different gas operatedrifles, carbines, pistols, and the like. Although embodiments arediscussed herein with respect to the M16/M4 and HK416, such discussionis by way of illustration only and not by way of limitation. Variousembodiments can be used with various gas operated firearms, includingrifles, carbines, and pistols.

One or more of the embodiments described herein can be used to modifystandard M16/M4 firearms. The embodiments can mitigate problems with theM16/M4 firearms and/or can enhance the performance of M16/M4 firearms.The embodiments tend to required little change to the production gun orits production tooling, so that an M16/M4 manufacturer can, withcomparatively little expense and effort, convert the fifty-two year olddesign of the M16 into a higher performance product. This higherperformance product can reliably fire the SureFire 60 and 100 round highcapacity magazines. These high capacity magazines provide one to threetimes the firepower of the present twenty shot standard magazines. Thus,such high capacity magazines can be used the without burning out the gastube, piston rings, or barrel gas port and without increasing the cyclerate beyond a point where the magazine can reliably feed. Suchembodiments can be provided with small, cheap, easy modifications tostandard M16 and M4 production parts.

More robust long lugs are provided so that the firearm can fire a morepowerful cartridge, such as the 6.8 mm cartridge. The 6.8 mm cartridgeapplies 1.3 times the force on the lugs as compared to the 5.56cartridge, which the firearm was originally designed to use. Theincreased surface are of the lugs is provided by lengthening the boltlugs and barrel extension lugs 1.35 times. This provides the greatershear area and longer feed ramps, as discussed herein.

The more robust locking lugs are provided without moving the breach ofthe barrel forward. Moving the breach of the barrel forward wouldundesirably either shorten the threaded length of the barrel and reducethe strength of the barrel attachment to the barrel extension or wouldrequire a longer barrel extension which would need an unwanted change tothe main gun body.

Rather, according to an embodiment, the barrel extension's inner lengthand overall length are changed, while leaving the outer length of therearward face to the flange the same. No change to the main gun body,barrel nut assembly and forward assembly, sight block or gas tube isneeded.

The features described herein can be used individually or in any desiredcombination to provide a safer, more reliable firearm. One or more ofthese features can be used to modify an existing firearm. One or more ofthese features can be used to manufacture a new firearm.

Comparisons are made herein to the standard M16. For such comparisons,the standard M16 can be the M16 manufactured by FN Manufacturing LLC(FNM), PO Box 24257, Columbia, S.C. 29224.

Comparisons are made herein to the standard M4. For such comparisons,the standard M4 can be the M4 carbine manufactured by Colt'sManufacturing Company Inc., Firearms Division PO Box 1868, Hartford,Conn. 06144.

The standard M16 can be that defined by any M16 rifle Technical DataPackage (TDP) adopted by the US Military as the standard for the M16rifle, M4 carbine, or AR15 civilian model. The standard M4 can be thatdefined by an M4 carbine TDP adopted by the US Military as the standardwhen features differ from those of the M16 rifle TDP.

A firearm can comprise: a bolt having a plurality of locking lugs, thelocking lugs being configured to have a shear area that is at leastapproximately 1.3 times that of a standard M16/M4; a piston formed onthe bolt and having a plurality of rings configured to cooperate withthe piston to mitigate gas leakage past the piston, each of the ringshaving a key formed thereon and a gap formed therein such that the gapof one ring is configured to receive at least a portion of the key ofanother ring; a bolt carrier to which the bolt is movably attached, thebolt carrier having a double cut cam, the double cut cam having astarting point in an unlocked position of the bolt that is substantiallythe same as the standard M16 cam and having an unlocking cam surfacethat has sufficient dwell increase to delay a start of unlocking whenthe bolt carrier is used in an M16/M4 rifle or carbine; a weight movablydisposed within the bolt carrier, the weight being configured to inhibitrearward and forward bouncing of the bolt carrier; a carrier keyattached to the bolt carrier and configured to facilitate a stroke ofthe bolt carrier that is approximately 0.360 inch longer than that ofthe standard M16/M4; a buffer having a length that is approximately0.360 inch shorter than a standard buffer for the M16 /M4 buffer; a tubeconfigured to provide gas from a barrel of the firearm to the piston viathe carrier key, the tube having a heat radiator formed on at least aportion of the tube; a gas metering plug having a gas metering holeconfigured to meter gas from the barrel of a firearm to the bolt carrierof the firearm, wherein the gas metering hole is located away from a gasport of the firearm; and a front sight block having a rear band and afront band for attaching the sight block to the barrel and having a gaspassage formed in the front band for facilitating gas flow from thebarrel to a gas tube of the firearm.

A bolt group can comprise: a bolt having a plurality of locking lugs,the locking lugs being configured to have a shear area that is at leastapproximately 1.3 times that of a standard M16/M4; a piston formed onthe bolt and having a plurality of rings configured to cooperate withthe piston to mitigate gas leakage past the piston, each of the ringshaving a key formed thereon and a gap formed therein such that the gapof one ring is configured to receive at least a portion of the key ofanother ring; a bolt carrier to which the bolt is movably attached, thebolt carrier having a double cut cam, the double cut cam having astarting point in an unlocked position of the bolt that is substantiallythe same as the standard M16 cam and having an unlocking cam surfacethat has sufficient dwell increase to delay a start of unlocking whenthe bolt carrier is used in an M16 rifle or an M4 carbine; a weightmovably disposed within the bolt carrier, the weight being configured toinhibit rearward and forward bouncing of the bolt carrier; and a carrierkey attached to the bolt carrier and configured to facilitate a strokeof the bolt carrier that is approximately 0.360 inch longer than that ofthe standard M16/M4.

A device can comprise: a ring configured to cooperate with a piston of agas operated firearm to mitigate gas leakage past the piston; a keyformed upon the ring; and a gap formed in the ring and configured toreceive at least a portion of a key of another ring; wherein the key issubstantially opposite the gap on the ring; wherein the key and the gapare formed such that a pair of the rings is nestable with the key ofeach of the rings disposed within the gap of each other of the rings;wherein the key is substantially rectangular in cross-section; whereinthe gap is substantially rectangular in cross-section; wherein the wallsof the ring are substantially rectangular in cross-section; wherein thering is formed of stainless steel; wherein the ring is configured to bereceived at least partially within a groove of the piston; wherein thedevice is a firearm.

A device can comprise: a piston for a gas operated firearm; a first ringconfigured to be received on the piston; a second ring configured to bereceived on the piston; and wherein the first ring and second ring areconfigured to interlock with one another such that the first ring andsecond ring rotate substantially in unison about the piston.

A method can comprise: placing one ring having a key and a gap on apiston of a gas operated firearm; placing another ring having a key anda gap on the piston; and wherein the key of each one of the rings isdisposed at least partially within the gap of each of the other rings.

A method can comprise: mitigating gas leakage past a piston of a firearmusing a plurality of rings, each one of the rings having a key formedthereon and a gap formed therein; and wherein the gap of one of therings receives at least a portion of the key of another of the rings.

A device can comprise: a tube configured to provide gas from a barrel ofa firearm to a piston of the firearm via the carrier key; and a heatradiator extending from at least a portion of the tube; wherein the heatradiator comprises fins that form a V-notch with approximately 60degrees between opposing walls; wherein the heat radiator comprisesthreads;

The device wherein the tube has an outer diameter of 0.250 inch; whereinthe tube is formed of 347 stainless steel; wherein the tube isconfigured for use on a firearm having a piston formed on a bolt of thefirearm; wherein the tube is configured for use on a member of an M16/M4family of firearms; wherein the tube is configured to receive gas from abarrel of a firearm that is a member of an M16/M4 family of firearms viaa front sight of the firearm and to provide the gas to a bolt carrier ofthe firearm via a bolt carrier key, the tube having an outsideinterfacing diameter to the bolt carrier key of less than 0.1792 inches,the tube having a length from a front sight mounting hole thereof to arear end thereof of less than 9.57 inches for an M4 type of firearm, andthe tube having a length from a front sight mounting hole thereof to arear end thereof of less than 14.95 inches for an M16 type of firearm;wherein the device is a firearm; wherein the threads are a uniformstandard thread form; wherein the threads comprises helical threads.Therefore, thermal expansion clearance for sustained full auto fire withsuccessive 60 and 100 round high capacity magazines is ensured.

A method can comprise: cutting a tube; forming a radiator on the tube;and installing the tube on a firearm such that the tube is configured toprovide gas from a barrel of the firearm to a piston thereof; forming afirst bend in the tube; and forming a second bend in the tube; whereinthe heat radiator comprises threads; wherein the threads are uniformstandard thread form; wherein the threads are formed on a portion of thetube away from ends of the tube; wherein the threads are not formed onends of the tube; wherein the tube has an outer diameter of 0.250 inch;wherein the tube is formed of 347 stainless steel.

A device can comprise a tube configured to receive gas from a barrel ofa firearm that is a member of an M16/M4 family of firearms via a frontsight of the firearm and to provide the gas to a bolt carrier of thefirearm via a bolt carrier key, the tube having an outside interfacingdiameter to the bolt carrier key of less than 0.1792 inches to insurethermal expansion clearance for sustained full auto fire with successive60 and 100 round high capacity magazines.

A device can comprise a tube configured to receive gas from a barrel ofa firearm that is a member of an M4 family of firearms via a front sightof the firearm and to provide the gas to a bolt carrier of the firearmvia a bolt carrier key, the tube having a length from a front sightmounting hole thereof to a rear end thereof of less than 9.57 inches toinsure thermal expansion clearance for sustained full auto fire withsuccessive 60 and 100 round high capacity magazines.

A device can comprise a tube configured to receive gas from a barrel ofa firearm that is a member of an M16 family of firearms via a frontsight of the firearm and to provide the gas to a bolt carrier of thefirearm via a bolt carrier key, the tube having a length from a frontsight mounting hole thereof to a rear end thereof of less than 14.95inches to insure thermal expansion clearance for sustained full autofire with successive 60 and 100 round high capacity magazines.

A method can comprise: providing gas from a barrel of a firearm to apiston of the firearm; and wherein a heat radiator extends from at leasta portion of the tube.

A device can comprise: a gas metering hole configured to meter gas froma barrel of a firearm to a bolt carrier of the firearm; and wherein thegas metering hole is located away from a gas port of the firearm;wherein the gas metering hole is located sufficiently away from the gasport of the firearm so as to be substantially unaffected by erosion;wherein the gas metering hole is located sufficiently away from the gasport of the firearm so as to be substantially unaffected by erosioncaused by scrubbing of passing bullets and/or bombardment of propellantgrains; wherein the gas metering hole is configured such that gas passestherethrough prior to entering a gas tube of the firearm; wherein thegas metering hole is smaller than a gas port of the firearm; wherein thegas metering hole is formed in a plug at a front of a gas tube; whereinthe gas metering hole is formed of a heat resistant material; whereinthe device is a firearm.

A method can comprise: placing a gas metering hole in a path of gas froma barrel of a firearm to a bolt carrier of the firearm; wherein the gasmetering hole is located away from a gas port of the firearm; andwherein the gas metering hole is configured to meter gas.

A method can comprise: metering gas from a barrel of a firearm through agas metering hole; providing the gas to a bolt carrier of the firearm;and wherein the gas metering hole is located away from a gas port of thefirearm.

A device can comprise: a front sight block for a firearm; a rear bandand a front band for attaching the sight block to a barrel of thefirearm; and a gas passage formed in the front band for facilitating gasflow from the barrel to a gas tube of the firearm; the device whereinthe gas passage is configured to substantially align with a gas port ofthe barrel and to receive gas from the gas port; can comprise a gasmetering plug configured to be received within the front sight block andconfigured to meter gas from the gas port; wherein the gas metering plugcomprises a fixed orifice; wherein the gas metering plug comprises acalibrated orifice; can comprise a gas tube configured to mate with thefront sight block; can comprise a heat exchanger formed upon the gastube; can comprise threads formed upon the gas tube; wherein the frontsight block is configured for use with a member of the M16/M4 family offirearms; wherein the device is a firearm.

A method can comprise: forming a gas passage in a front band of a frontsight block; forming a gas port in a barrel; and attaching the frontsight block to the barrel such that the gas passage is substantiallyaligned with respect to the gas port; the device can comprise installinga gas metering plug in the front sight block; the device can comprisecan comprise installing a gas metering plug in the gas tube andinstalling the gas tube partially within the front sight block.

A method can comprise: communicating gas from a barrel of a firearm to agas tube of the firearm; and wherein the gas is communicated through afront band of a front sight block; the device can comprise metering gasthrough a gas metering plug.

A device can comprise: a bolt carrier; a double cut cam formed in thebolt carrier; and wherein the cam has a starting point in an unlockedposition of the bolt that is substantially the same as the standard M16cam and has an unlocking cam surface that has sufficient dwell increaseto delay a start of unlocking when the bolt carrier is used in an M16rifle or an M4 carbine; wherein the device is a firearm.

A method can comprise: assembling a bolt carrier into a firearm; whereina double cut cam is formed in the bolt carrier; and wherein the doublecut cam has a starting point in an unlocked position of the bolt that issubstantially the same as the standard M16 cam and has an unlocking camsurface that has sufficient dwell increase to delay a start of unlockingwhen the bolt carrier is used in an M16 rifle or an M4 carbine.

A method can comprise: moving a double cut cam with respect to a cam pinfrom an unlocked position of a bolt to a locked position of the bolt;and wherein the double cut cam has a starting point in the unlockedposition of the bolt that is substantially the same as the standard M16cam and has an unlocking cam surface that has sufficient dwell increaseto delay a start of unlocking when the bolt carrier is used in an M16rifle or an M4 carbine.

A device can comprise: a bolt carrier; a weight movably disposed withinthe bolt carrier; and wherein the weight is configured to inhibitrearward and forward bouncing of the bolt carrier; wherein the weight isconfigured to slide within the bolt carrier; wherein the weight isconfigured to impact an anvil after the bolt carrier begins to bounceaway from a forwardmost position of the bolt carrier so as to inhibitbouncing of the bolt carrier; wherein the weight is configured to impactan anvil after the bolt carrier begins to bounce away from arearwardmost position of the bolt carrier so as to inhibit bouncing ofthe bolt carrier; wherein the weight is configured to impact an anvilafter a bolt engages bolt lugs of a firearm so as to inhibit bouncing ofthe bolt carrier; wherein the weight is configured to impact an anvilafter a buffer of the bolt carrier contacts a rear wall of a receiver ofa firearm so as to inhibit bouncing of the bolt carrier; the device cancomprise: a cavity formed within the bolt carrier and within which theweight slides; and at least one spring configured to generally centerthe weight within the cavity; the device can comprise: a cavity formedwithin the bolt carrier and within which the weight slides; two springsconfigured to generally center the weight within the cavity; and twoplungers upon which the springs are disposed; wherein the weight isgenerally cylindrical in shape; the device can comprise: a first cavityformed within the bolt carrier and within which the weight slides; twosprings configured to generally center the weight within the firstcavity; two plungers upon which the springs are disposed; a secondcavity and a third cavity formed within the weight, one spring and oneplunger being disposed within each of the second cavity and the thirdcavity; and wherein the second cavity and the third cavity have blockingshoulders that prevent the plunger disposed therein from moving beyond acentered position of the plunger so that when inertia moves the weightbeyond a centered position of the weight one plunger compresses a springto return the weight to center while the other plunger and spring areblocked from acting upon the weight; The device as recited in claim 76,further can comprise an anvil configured to hold the weight, thesprings, and the plungers within the bolt carrier; wherein the weight isconfigured to impact against the anvil during forward and rearwardtravel of the weight; the device can comprise a pin configured to holdthe anvil at least partially within the bolt carrier; wherein the boltcarrier is configured for use in a firearm selected from the groupconsisting of: a member of an M16/M4 family of firearms; a copy of amember of an M16/M4 family of firearms; and any firearm in which thebolt carrier will function; wherein the bolt carrier is modified tofunction in guns that are driven by an operating rod and piston; whereinthe device is a firearm.

A method can comprise: providing a bolt carrier; movably disposing aweight within the bolt carrier; and wherein the weight is configured toinhibit rearward and forward bouncing of the bolt carrier; wherein theweight is configured to slide within the bolt carrier; wherein theweight is configured to impact an anvil after the bolt carrier begins tobounce away from a forwardmost position of the bolt carrier so as toinhibit bouncing of the bolt carrier; wherein the weight is configuredto impact an anvil after the bolt carrier begins to bounce away from arearwardmost position of the bolt carrier so as to inhibit bouncing ofthe bolt carrier; wherein the weight is configured to impact an anvilafter the bolt engages bolt lugs of a firearm so as to inhibit bouncingof the bolt carrier; wherein the weight is configured to impact an anvilafter a buffer of the bolt carrier contacts a rear wall of a receiver ofa firearm so as to inhibit bouncing of the bolt carrier; the device cancomprise: forming a cavity formed within the bolt carrier such that theweight is slidable with the cavity; and centering the weight within thecavity using at least one spring; the device can comprise: forming afirst cavity within the bolt carrier such that the weight is slidablewith the first cavity; centering the weight within the first cavityusing two springs that are disposed upon two plungers; and wherein theweight comprises a second cavity and the third cavity that each have oneof the plungers and one of the springs disposed therein and that haveblocking shoulders that prevent the plunger disposed therein from movingbeyond a centered position of the plunger so that when inertia moves theweight beyond a centered position of the weight one plunger compresses aspring to return the weight to center while the other plunger and springare blocked from acting upon the weight; wherein the weight is generallycylindrical in shape; the device can comprise: forming a first cavitywithin the bolt carrier such that the weight is slidable with the firstcavity; forming a second cavity and a third cavity within the weight;centering the weight within the first cavity using two springs that aredisposed upon two plungers; wherein one of the springs and one of theplungers are disposed within each of the second cavity and the thirdcavity; and wherein the second cavity and the third cavity have blockingshoulders that prevent the plunger disposed therein from moving beyond acentered position of the plunger so that when inertia moves the weightbeyond a centered position of the weight one plunger compresses a springto return the weight to center while the other plunger and spring areblocked from acting upon the weight; the device can comprise using ananvil to hold the weight, the springs, and the plungers within the boltcarrier; wherein the weight is configured to impact against the anvilduring forward and rearward travel of the weight; the device cancomprise using a pin to hold the anvil at least partially within thebolt carrier; wherein the bolt carrier is configured for use in a memberof an M16/M4 family of firearms.

A method can comprise: firing a firearm so as to cause a weight to movewithin a bolt carrier; and wherein the weight is configured to inhibitrearward and forward bouncing of the bolt carrier; wherein the weight isconfigured to slide within the bolt carrier; wherein the weight isconfigured to impact an anvil after the bolt carrier begins to bounceaway from a forwardmost position of the bolt carrier so as to inhibitbouncing of the bolt; wherein the weight is configured to impact ananvil after the bolt carrier begins to bounce away from a rearwardmostposition of the bolt carrier so as to inhibit bouncing of the boltcarrier; wherein the weight is configured to impact an anvil after thebolt engages bolt lugs of a firearm so as to inhibit bouncing of thebolt carrier; wherein the weight is configured to impact an anvil aftera buffer of the bolt carrier contacts a rear wall of a receiver of afirearm so as to inhibit bouncing of the bolt carrier; wherein: theweight slides within a cavity formed within the bolt carrier; and atleast one spring generally centers the weight within the cavity;wherein: the weight slides within a cavity formed within the boltcarrier; two springs generally center the weight within the cavity; thetwo springs are disposed within two cavities upon two plungers; andwherein the two cavities have blocking shoulders that prevent theplunger disposed therein from moving beyond a centered position of theplunger so that when inertia moves the weight beyond a centered positionof the weight one plunger compresses one spring to return the weight tocenter while the other plunger and the other spring are blocked fromacting upon the weight; wherein the weight is generally cylindrical inshape; wherein: the weight slides within a first cavity formed withinthe bolt carrier; two springs generally center the weight within thefirst cavity; the two springs are disposed upon two plungers; one of thesprings and one of the plungers are disposed within each of a secondcavity and a third cavity formed in the weight; and wherein the secondcavity and the third cavity have blocking shoulders that prevent theplunger disposed therein from moving beyond a centered position of theplunger so that when inertia moves the weight beyond a centered positionof the weight one plunger compresses a spring to return the weight tocenter while the other plunger and spring are blocked from acting uponthe weight; the device can comprise holding the weight, the springs, andthe plungers within the bolt carrier using an anvil; wherein the weightis configured to impact against the anvil during forward and rearwardtravel of the weight; the device can comprise holding the anvil at leastpartially within the bolt carrier using a pin; wherein the bolt carrieris configured for use in a member of an M16/M4 family of firearms.

A device can comprise a bolt carrier having a weight disposed therein soas to inhibit both forward and rearward bouncing of the bolt carrier.

A method can comprise sliding a weight within a bolt carrier so as toinhibit both forward and rearward bouncing of the bolt carrier.

A device can comprise: a bolt for an M16/M4 firearm, the bolt cancomprise: a plurality of locking lugs formed upon the bolt; a barrelextension; a plurality of locking lugs formed upon the barrel extension;wherein the locking lugs are configured to have a shear area that is atleast approximately 1.3 times that of a standard M16/M4; wherein theshear area is increased with respect to that of a standard M16/M4 bylengthening the locking lugs; the device can comprise: a flange formedupon the barrel extension such that the flange is approximately 0.130inch from a forward end of the barrel extension; a carrier keyconfigured to facilitate a stroke of a bolt carrier within which thebolt is partially disposed, the carrier key being approximately 0.360inch longer than that of a standard M16/M4; and a buffer having a lengththat is approximately 0.360 inch shorter buffer than a standard bufferfor the M16 /M4 buffer; wherein the device is a firearm.

A bolt group can comprise: a bolt having a plurality of locking lugs;and wherein the locking lugs are configured to have a shear area that isat least approximately 1.3 times that of a standard M16/M4; wherein theshear area is increased with respect to that of the standard M16/M4 bylengthening the locking lugs; the device can comprise: a bolt catch; andwherein an over travel of the bolt catch is approximately 0.355 inch soas to provide sufficient time for the bolt catch to engage in an eventof increased fire rate; wherein a travel of the bolt is increased by0.360 inch with respect to the travel of the standard M16/M4 to reduce arate of fire of a firearm.

A method can comprise: assembling a bolt for an M16/M4 firearm into thefirearm; and wherein the bolt comprises a plurality of locking lugsconfigured to have a shear area that is at least approximately 1.3 timesthat of a standard M16/M4.

A method for operating a firearm, the method can comprise: engaginglocking lugs of a bolt with complementary locking lugs of a barrelextension; and wherein the locking lugs of the bolt and the locking lugsof the barrel extension are configured to have a shear area that is atleast approximately 1.3 times that of the shear area of a standardM16/M4; wherein the shear area is increased with respect to that of thestandard M16/M4 by lengthening the locking lugs; the device can comprisemoving the bolt with an over travel of the bolt catch of approximately0.355 inch so as to provide sufficient time for the bolt catch to engagein the event of increased gas pressure, firing rate, or bolt grouptravel speed; the device can comprise moving the bolt with a travel thatis increased by 0.360 inch with respect to the travel of the standardM16/M4 to reduce a rate of fire of a firearm; the device can comprisefeeding cartridges via two feed ramps that are longer and wider thanfeed ramps of the standard M16/M4; the device can comprise unlocking thebolt after approximately the same delay and at approximately the samepressure drop as that of the standard M16 using a double cut cam.

A device can comprise: a carrier key configured to facilitate a strokeof the bolt carrier that is approximately 0.360 inch longer than that ofa standard M16/M4; and a buffer having a length that is approximately0.360 inch shorter buffer than a standard buffer for the M16 /M4 buffer;wherein the carrier key is configured to attach to a bolt carrier withonly one fastener; wherein the carrier key is configured to avoidinterference with a portion of a lower receiver when the carrier and keyare in a rearmost position; wherein the device is a firearm.

A method can comprise: attaching a carrier key to a bolt carrier for anM16/M4 firearm, wherein the carrier key is configured to facilitate astroke of the bolt carrier that is approximately 0.360 inch longer thanthat of a standard M16/M4; and placing a buffer in the firearm, thebuffer having a length that is approximately 0.360 inch shorter bufferthan a standard buffer for the M16/ M4 buffer.

A method can comprise: cycling a bolt carrier for an M16/M4 firearm,wherein the carrier key is configured to facilitate a stroke of the boltcarrier that is approximately 0.360 inch longer than that of a standardM16/M4; and wherein the bolt carrier abuts a buffer having a length thatis approximately 0.360 inch shorter buffer than a standard buffer forthe M16/M4 buffer.

Embodiments described above illustrate, but do not limit, the invention.It should also be understood that numerous modifications and variationsare possible in accordance with the principles of the present invention.Accordingly, the scope of the invention is defined only by the followingclaims.

What is claimed is:
 1. A gas tube for a firearm, the gas tubecomprising: a tube configured to provide gas from a barrel of thefirearm to a piston of the firearm via a carrier key attached to a boltcarrier of the firearm; and a heat radiator formed on at least a portionof the tube.